Bulk acoustic wave filter and method for manufacturing the same

Abstract

The present disclosure provides a bulk acoustic wave filter and a method for preparing the same. The bulk acoustic wave filter includes a substrate, a resonant structure, a bottom electrode structure, and a cover plate structure. The resonant structure is disposed in the middle of the substrate; the bottom electrode structure is disposed on the surface of the substrate and covers the resonant cavity of the resonant structure; the cover plate structure is bonded to the bottom electrode structure to seal the resonant structure in a sealed space between the cover plate structure and the substrate. Compared with the structural design in the prior art in which the bottom electrode structure is recessed in the groove of the substrate, by directly forming the bottom electrode structure on the upper surface of the substrate, the processes such as etching the groove of the substrate are omitted, the number of micro-cap wafer processing layers and the processing steps are simplified, the cost is greatly reduced, and at the same time, the device performance and device quality of the bulk acoustic wave filter can be guaranteed.

Description

Technical Field

[0001] The present disclosure relates to the field of semiconductor process technology, and in particular to a bulk acoustic wave filter and a preparation method thereof. Background Art

[0002] With the continuous development of 5G technology, the application and demand of RF filters are constantly upgraded, and the performance indicators of RF filters are required to be higher and higher. Generally, according to the transmission method of sound waves in RF filters, RF filters are divided into: bulk acoustic wave filters and surface acoustic wave filters. Among them, surface acoustic wave filters generally operate below 2.5G frequency, and bulk acoustic wave filters operate at 1.5G~10G frequency. In comparison, thin film bulk acoustic wave filters have outstanding performance in high performance, high reliability, and high power carrying, but their cost is also high, which seriously restricts their competitiveness in the market with surface acoustic wave filters and other types of filters.

[0003] The existing sealing method of thin film bulk acoustic wave resonator generally adopts wafer-level gold-gold hot compression bonding to seal the device and isolate it from the outside. The principle of wafer-level gold-gold hot compression bonding is achieved through high temperature and high pressure. It requires higher pressure and has higher requirements on the flatness and coplanarity of the bonding surfaces of the two wafers. At the same time, it also puts forward higher requirements on the bonding equipment. The usual method is to design a special structure on the micro-cap to improve the bonding effect.

[0004] For wafer-level bonding, it is difficult to obtain a high bonding yield. In order to ensure the bonding yield of the entire wafer, the coplanarity of the bonded wafer is required to be high. The sealing area of ​​the thin film bulk acoustic wave resonator needs to retain the bottom electrode of the device on the substrate to achieve good consistency in the coplanarity between the bonding electrode in the functional area and the bonding electrode in the sealing area. In addition, for RF consumer electronics of thin film bulk acoustic wave resonators, while reducing costs, it is also required that the device performance and quality of the filter should not be reduced. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In order to solve at least one of the technical problems existing in the device packaging process of a thin film bulk acoustic wave filter through a wafer-level gold-gold thermocompression bonding process in the prior art, the present disclosure provides a bulk acoustic wave filter and a preparation method thereof.

[0007] (II) Technical solution

[0008] One aspect of the present disclosure provides a bulk acoustic wave filter, which includes a substrate, a resonant structure, a bottom electrode structure and a cover plate structure. The resonant structure is arranged in the middle of the substrate; the bottom electrode structure is arranged on the surface of the substrate and covers the resonant cavity of the resonant structure; the cover plate structure is bonded to the bottom electrode structure to seal the resonant structure in a sealed space between the cover plate structure and the substrate.

[0009] According to an embodiment of the present disclosure, the bottom electrode structure includes an adhesion layer and a bottom electrode layer. The adhesion layer is disposed on the upper surface of the substrate and covers the resonant cavity; the bottom electrode layer is disposed on the upper surface of the adhesion layer; wherein the adhesion layer and the bottom electrode layer constitute a bottom electrode pattern structure.

[0010] According to an embodiment of the present disclosure, the bottom electrode structure further includes a sealing bonding portion and a plurality of supporting bonding portions. The sealing bonding portion is provided along the edge of the upper surface of the substrate in an annular sealing manner to form a sealed space; and the plurality of supporting bonding portions surround the resonant structure and are distributed and provided on the upper surface of the substrate to support the sealed space.

[0011] According to an embodiment of the present disclosure, the sealing bonding portion includes at least one first sealing wall and at least two second sealing walls. The at least two second sealing walls sandwich at least one first sealing wall; wherein the at least two second sealing walls and the at least one first sealing wall are both closed annular structures protruding along the edge of the upper surface of the substrate, the thickness of the second sealing wall is greater than or equal to the thickness of the first sealing wall, and there is a gap between adjacent first sealing walls and second sealing walls.

[0012] According to an embodiment of the present disclosure, the sealing bonding portion also includes a sealing body, which covers at least one first sealing wall and at least two second sealing walls in an annular manner along the edge of the upper surface of the substrate, wherein the sealing body includes a sealing gap, which is recessed on the upper surface of the sealing body corresponding to the gap between adjacent first sealing walls and second sealing walls.

[0013] According to an embodiment of the present disclosure, the supporting bonding portion includes a supporting body, which is arranged on the upper surface of the bottom electrode layer, wherein the supporting body includes a supporting groove, which corresponds to the upper surface of the bottom electrode layer and is recessed on the upper surface of the supporting body.

[0014] According to an embodiment of the present disclosure, the resonant structure includes a piezoelectric layer, a top electrode layer and a frequency modulation layer. The piezoelectric layer is partially disposed on the upper surface of the substrate, and the other part is disposed on the upper surface of the bottom electrode layer, covering the resonant cavity; the top electrode layer corresponds to the resonant cavity and is disposed on the upper surface of the piezoelectric layer; and the frequency modulation layer is disposed on the upper surface of the top electrode layer.

[0015] According to an embodiment of the present disclosure, the piezoelectric layer includes a plurality of first openings and a plurality of second openings. The plurality of first openings correspond to a plurality of first support bodies of a plurality of support bonding parts, and each of the plurality of first support bodies passes through the first opening and is arranged on the upper surface of the bottom electrode layer; the plurality of second openings correspond to a plurality of second support bodies of a plurality of support bonding parts, and each of the plurality of second support bodies passes through the second opening and is arranged on the upper surface of the bottom electrode layer.

[0016] According to an embodiment of the present disclosure, the resonant cavity is recessed on the upper surface of the substrate.

[0017] According to an embodiment of the present disclosure, the cover plate structure includes a cover plate, a cover plate bonding portion and a first bonding layer. The cover plate bonding portion corresponds to a sealing body of the sealing bonding portion, and an annular sealing protrusion is arranged along the edge of the lower surface of the cover plate to cooperate with the substrate to form a sealed space; the first bonding layer is arranged on the top surface of the cover plate bonding portion and contacts with the upper surface of the sealing body.

[0018] According to an embodiment of the present disclosure, the cover plate structure further includes a plurality of cover plate bonding pillars and a plurality of second bonding layers. The plurality of cover plate bonding pillars correspond to the support bodies of the plurality of support bonding parts and are arranged in the support grooves of the support bodies; the plurality of second bonding layers correspond to the top surfaces of the plurality of cover plate bonding pillars and contact the bottom surfaces of the support grooves of the plurality of support bonding parts.

[0019] According to an embodiment of the present disclosure, the cover plate structure further includes a plurality of electrode holes and a plurality of back electrode layers. The plurality of electrode holes correspond to the plurality of cover plate bonding pillars and penetrate the plurality of cover plate bonding pillars; the plurality of back electrode layers correspond to the plurality of electrode holes and are arranged on the upper surface of the cover plate; wherein each of the plurality of back electrode layers passes through each of the plurality of electrode holes and contacts the support body.

[0020] Another aspect of the present disclosure provides a method for preparing the above-mentioned bulk acoustic wave filter, which includes: forming a resonant structure located in the middle position of the substrate on a substrate; forming a bottom electrode structure located on the surface of the substrate and covering the resonant cavity of the resonant structure according to the resonant structure; and sealing the resonant structure in a sealed space between the cover structure and the substrate by bonding the cover structure and the bottom electrode structure.

[0021] According to an embodiment of the present disclosure, in forming a bottom electrode structure of a resonant cavity located on a surface of a substrate and covering the resonant structure according to a resonant structure, it includes: forming an adhesion layer covering the resonant cavity of the resonant structure on the upper surface of the substrate; and forming a bottom electrode layer on the upper surface of the adhesion layer.

[0022] (III) Beneficial effects

[0023] The present disclosure provides a bulk acoustic wave filter and a method for preparing the same. The bulk acoustic wave filter includes a substrate, a resonant structure, a bottom electrode structure, and a cover plate structure. The resonant structure is disposed in the middle of the substrate; the bottom electrode structure is disposed on the surface of the substrate and covers the resonant cavity of the resonant structure; the cover plate structure is bonded to the bottom electrode structure to seal the resonant structure in a sealed space between the cover plate structure and the substrate. Compared with the structural design in the prior art in which the bottom electrode structure is recessed in the groove of the substrate, by directly forming the bottom electrode structure on the upper surface of the substrate, the processes such as etching the groove of the substrate are omitted, the number of micro-cap wafer processing layers and the processing steps are simplified, the cost is greatly reduced, and at the same time, the device performance and device quality of the bulk acoustic wave filter can be guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A cross-sectional view schematically shows the structure of a bulk acoustic wave filter according to an embodiment of the present disclosure;

[0025] Figure 2 Schematically shows the corresponding Figure 1 A cross-sectional view of the structure of the substrate 100 and the resonant cavity 201 of the BAW filter;

[0026] Figure 3 Schematically shows the corresponding Figure 2 A cross-sectional view of the structure of the resonant cavity 201 filled with a sacrificial layer 510;

[0027] Figure 4 Schematically shows the corresponding Figure 3 A cross-sectional view of the structure of the resonant cavity 201 covered with an adhesion layer 310 and a bottom electrode layer 320;

[0028] Figure 5 Schematically shows the corresponding Figure 4 A cross-sectional view of the structure composition of the patterned structure of the adhesion layer 310 and the bottom electrode layer 320 of the structure shown;

[0029] Figure 6 Schematically shows the corresponding Figure 5 A top view of the structural composition of the patterned structure of the structure shown, wherein region B is a functional region of the resonant structure 200 having multiple resonant cavities 201 not covered by the bottom electrode structure 300;

[0030] Figure 7 Schematically shows the corresponding Figure 6 A top view of the structural composition of region A of the patterned structure of the structure shown;

[0031] Figure 8Schematically shows the corresponding Figure 5 A cross-sectional view of the structure of the piezoelectric layer 210 of the resonant structure 200 of the structure shown;

[0032] Fig. 9 Schematically shows the corresponding Figure 8 A cross-sectional view of the structure of the top electrode layer 220 and the frequency modulation layer 230 of the resonance structure 200;

[0033] Fig.10 Schematically shows the corresponding Fig. 9 A cross-sectional view of the structure of the patterned piezoelectric layer 210 of the resonant structure 200 of the structure shown;

[0034] Fig.11 Schematically shows the corresponding Fig.10 A cross-sectional view of the structure of the sealing body 333 and the supporting body 341 of the resonance structure 200 of the structure shown;

[0035] Fig.12 Schematically shows the corresponding Fig.11 A cross-sectional view of the structural composition of the C region of the structure shown;

[0036] Fig.13 Schematically shows the corresponding Figure 1 A cross-sectional view of the structural composition of a cover plate 410 of a cover plate structure 400 of a bulk acoustic wave filter;

[0037] Fig.14 Schematically shows the corresponding Fig.13 A cross-sectional view of the structure of the electrode hole 402 of the cover plate structure 400;

[0038] Fig.15 Schematically shows the corresponding Fig.14 A cross-sectional view of the structure of the first bonding layer 430 and the second bonding layer 450 of the cover structure 400;

[0039] Fig.16 Schematically shows the corresponding Fig.15 The cover plate structure 400 and Fig.11 The cross-sectional view of the structure of the bottom electrode structure 300 after bonding;

[0040] Fig.17 Schematically shows the corresponding Fig.16 The structural composition cross-sectional view of the bonding structure after the cover plate 410 thinning process is performed;

[0041] Fig.18 Schematically shows the corresponding Fig.17 A cross-sectional view of the structure of the back electrode layer 460 of the cover structure shown;

[0042] Fig.19 Schematically shows the corresponding Figure 2-Figure 18 Flow chart of a method for preparing a bulk acoustic wave filter shown. DETAILED DESCRIPTION

[0043] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0044] It should be noted that the implementation methods not shown or described in the drawings or the text of the specification are all forms known to ordinary technicians in the relevant technical field and are not described in detail. In addition, the above definitions of various elements and methods are not limited to the various specific structures, shapes or methods mentioned in the embodiments, and ordinary technicians in the field can simply change or replace them.

[0045] It should also be noted that the directional terms mentioned in the embodiments, such as "upper", "lower", "front", "back", "left", "right", etc., are only reference directions of the drawings and are not intended to limit the scope of protection of the present disclosure. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or configurations will be omitted when they may cause confusion in the understanding of the present disclosure.

[0046] Moreover, the shapes and sizes of the components in the figures do not reflect the real size and proportion, but only illustrate the contents of the embodiments of the present disclosure. In addition, in the claims, any reference symbols between brackets shall not be constructed as limiting the claims.

[0047] Furthermore, the word "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0048] The ordinal numbers used in the specification and claims, such as "first", "second", "third", etc., to modify the corresponding elements, do not themselves mean that the elements have any ordinal numbers, nor do they represent the order of one element and another element or the order of manufacturing methods. The use of these ordinal numbers is only used to clearly distinguish a component with a certain name from another component with the same name.

[0049] Those skilled in the art will appreciate that the modules in the devices in the embodiments may be adaptively changed and set in one or more devices different from the embodiments. The modules or units or components in the embodiments may be combined into one module or unit or component, and in addition they may be divided into multiple submodules or subunits or subcomponents. All features disclosed in this specification (including the accompanying claims, abstracts and drawings) and all processes or units of any method or device disclosed in this manner may be combined in any combination, except that at least some of such features and / or processes or units are mutually exclusive. Unless otherwise expressly stated, each feature disclosed in this specification (including the accompanying claims, abstracts and drawings) may be replaced by an alternative feature that provides the same, equivalent or similar purpose. Furthermore, in a unit claim that lists several devices, several of these devices may be embodied by the same hardware item.

[0050] Similarly, it should be understood that in order to streamline the present disclosure and aid in understanding one or more of the various disclosed aspects, in the above description of the exemplary embodiments of the present disclosure, the various features of the present disclosure are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting the following intention: the claimed disclosure requires more features than the features explicitly recited in each claim. More specifically, as reflected in the claims below, the disclosed aspects lie in less than all the features of the single embodiment disclosed above. Therefore, the claims that follow the specific embodiment are hereby expressly incorporated into the specific embodiment, with each claim itself serving as a separate embodiment of the present disclosure.

[0051] In the existing wafer-level gold-gold hot-press bonding process for the device packaging of the FBAW filter, the bottom electrode is retained at the bottom of the sealing area of ​​the FBAW filter to ensure the coplanarity and flatness of the bonding plane. The bottom electrode is generally made of aluminum nitride material as an adhesion layer, and the release of the sacrificial layer during the processing of the entire device needs to be completed by hydrofluoric acid etching. However, aluminum nitride is a material with a large molecular pore size, and hydrofluoric acid molecules are relatively small compared to aluminum nitride. It can easily erode the adjacent bonding interface through the aluminum nitride material to form microchannels, resulting in the device's weak resistance to deteriorating conditions such as water vapor.

[0052] In order to solve at least one of the technical problems existing in the device packaging process of a thin film bulk acoustic wave filter through a wafer-level gold-gold thermocompression bonding process in the prior art, the present disclosure provides a bulk acoustic wave filter and a preparation method thereof.

[0053] like Figure 1As shown, one aspect of the present disclosure provides a bulk acoustic wave filter, which includes a substrate 100, a resonant structure 200, a bottom electrode structure 300 and a cover structure 400. The resonant structure 200 is arranged in the middle of the substrate 100; the bottom electrode structure 300 is arranged on the surface of the substrate 100 and covers the resonant cavity 201 of the resonant structure 200; the cover structure 400 is bonded to the bottom electrode structure 300 to seal the resonant structure 200 in the sealed space 101 between the cover structure 400 and the substrate 100.

[0054] The substrate 100 is used as the device support structure of the entire BAW filter. Correspondingly, the cover structure 400 and the substrate 100 constitute a wafer-level packaging structure of the BAW filter device, which seals the resonant structure 200, plays a role in base protection, and provides a stable working space for the resonant function of the resonant structure.

[0055] The resonant structure 200 is disposed in the middle of the upper surface of the substrate 100 as a device functional area to achieve a resonant function.

[0056] The bottom electrode structure 300 is directly disposed on the upper surface of the substrate, and the bottom electrode structure 300 covers the resonant cavity 201, and does not fill the resonant cavity 201, and does not interfere with the resonant function of the resonant cavity 201. Therefore, compared with the structural form of the prior art in which the bottom electrode is disposed based on the etched groove or through hole on the substrate 100, the formation process of the bottom electrode structure 300 will avoid the process of trench etching on the substrate, greatly simplifying the preparation process, thereby reducing the preparation cost, and there is no impact on the device performance and device quality.

[0057] Therefore, compared with the structural design in the prior art in which the bottom electrode structure is recessed in the groove of the substrate, by directly forming the bottom electrode structure on the upper surface of the substrate, the processes such as trench etching of the substrate are eliminated, the number of micro-cap wafer processing layers and the processing steps are simplified, the cost is greatly reduced, and at the same time the device performance and device quality of the bulk acoustic wave filter can be guaranteed.

[0058] like Figure 1-Figure 18 As shown, according to an embodiment of the present disclosure, the bottom electrode structure 300 includes an adhesion layer 310 and a bottom electrode layer 320. The adhesion layer 310 is disposed on the upper surface of the substrate 100 and covers the resonant cavity 201; the bottom electrode layer 320 is disposed on the upper surface of the adhesion layer 310; wherein the adhesion layer 310 and the bottom electrode layer 320 constitute a bottom electrode pattern structure.

[0059] The adhesion layer 310 and the bottom electrode layer 320 are etched together to form a patterned structure, forming a bottom electrode patterned structure. The patterned structure corresponds to the etching positions of the adhesion layer 310 and the bottom electrode layer 320, exposing the structure of the upper surface of the substrate 100, so that the structure filled into the etching position corresponding to the exposed surface performs fault isolation on the adhesion layer 310 and the bottom electrode layer 320, presenting a patterned structure, specifically as follows Figure 4-Figure 6 shown.

[0060] Among them, the adhesion layer 310 is located below the bottom electrode layer 320 and on the surface of the substrate 100. Compared with the structural design in the prior art that the bottom electrode structure is recessed in the groove of the substrate, the adhesion layer 310 can be directly in contact with the substrate 100. Therefore, during the processing of the entire device, when the sacrificial layer is released, even if a corrosion process such as hydrofluoric acid is used for the corrosion process, it can effectively prevent the corrosion liquid molecules from corroding the adhesion layer to form microchannels, resulting in a decrease in the overall quality of the device and poor resistance to deteriorating conditions such as water vapor.

[0061] At the same time, the bottom electrode layer 320 can also ensure the coplanarity and flatness of the bonding plane during the packaging process. The peripheral area where the bottom electrode structure 300 and the cover plate structure 400 are bonded together forms a sealing area, and the middle area of ​​the bonding connection forms a supporting area.

[0062] It can be seen that by canceling the groove design of the bottom electrode on the protective silicon substrate 100, the micro-cap processing process and difficulty are reduced. At the same time, by performing patterning on the sealing area of ​​the bottom electrode structure of the thin film bulk acoustic wave filter, the bonding electrode corresponding to the bottom electrode structure 300 for bonding to the cover structure 400 is in direct contact with the silicon substrate 100, isolating the corrosion of the bottom electrode adhesion layer material in the sealing area by corrosive liquids such as hydrofluoric acid, avoiding the formation of interface channels, thereby improving the reliability of the device as a whole.

[0063] Therefore, the BAW filter of the disclosed embodiment achieves a technical breakthrough in the prior art of forming a bottom electrode in a groove of a substrate to achieve device stability and miniaturization, and achieves a redesign of the bottom electrode structure of the entire device structure, which not only simplifies the device preparation process, but also can isolate the formation of interface channels, thereby improving the device reliability as a whole and maintaining the good resonance function of the device.

[0064] like Figure 1-Figure 18 As shown, according to an embodiment of the present disclosure, the bottom electrode structure 300 further includes a sealing bonding portion 330 and a plurality of supporting bonding portions 340. The sealing bonding portion 330 is provided along the edge of the upper surface of the substrate 100 in an annular sealing manner to form a sealed space 201; the plurality of supporting bonding portions 340 surround the resonant structure 200 and are distributed and provided on the upper surface of the substrate 100 to support the sealed space 201.

[0065] like Figure 6 , Figure 7 As shown, the sealing bonding part 330 is a closed annular sealing protrusion structure protruding from the upper surface of the substrate 100. When the sealing bonding part 330 and the cover plate structure 400 are bonded and sealed, a sealed space 201 can be formed between the cover plate structure 400 and the substrate 100. That is, the sealing bonding part 330 mainly plays the role of bonding and sealing.

[0066] like Figure 6 , Figure 1 As shown, the supporting bonding portion 340 is a supporting protrusion structure protruding from the upper surface of the substrate 100, which is a supporting column in the sealed space 201, the lower end of which contacts the upper surface of the substrate 100 and the upper end of which contacts the lower surface of the cover structure 400, and has multiple and is arranged as shown in FIG. Figure 6 The outer side of the B area and the inner side of the sealing bonding part 330 are evenly distributed on the substrate 100 to support the cover structure 400 and the substrate 100, so that the cover structure 400 and the substrate 100 are not easily deformed, thereby avoiding distortion of the sealing space 201 and preventing the resonance function of the resonance structure 200 from being affected.

[0067] like Figure 1-Figure 18 As shown, according to an embodiment of the present disclosure, the sealing bonding portion 330 includes at least one first sealing wall 331 and at least two second sealing walls 332. At least one first sealing wall 331 is sandwiched between the at least two second sealing walls 332; wherein, the at least two second sealing walls 332 and the at least one first sealing wall 331 are both closed annular structures protruding along the edge of the upper surface of the substrate 100, the thickness of the second sealing wall 332 is greater than or equal to the thickness of the first sealing wall 331, and there is a gap 301 between adjacent first sealing walls 331 and second sealing walls 332.

[0068] like Figure 4-Figure 5 As shown, after the thin film structure of the adhesion layer 310 and the bottom electrode layer 320 formed on the substrate 100 is patterned, a patterned structure of the bottom electrode structure 300 can be formed, wherein at least one first sealing wall 331 and at least two second sealing walls 332 of the sealing bonding part 330 can be formed.

[0069] like Figure 7 , Fig.12As shown, at least one first sealing wall 331 and at least two second sealing walls 332 are all closed annular protruding structures protruding from the upper surface of the substrate 100, and have a certain transverse thickness. The thickness b of the second sealing wall 332 is greater than or equal to the thickness d of the first sealing wall 331, and the gap 301 between the second sealing wall 332 and the adjacent first sealing wall 331 is maintained at the same time, and the thickness b of the second sealing wall 332 can also be greater than or equal to the width c of the gap 301, so that when the bonding process of the cover plate structure 400 and the bottom electrode structure 300 is performed, the pressure corresponding to the second sealing wall 332 and the first sealing wall 331 is inconsistent, and the pressure at the first sealing wall 331 is greater, thereby ensuring that the bonding strength of the sealing bonding part 330 is better, thereby achieving better bonding sealing and stability, and improving the overall device structure quality.

[0070] like Figure 1-Figure 18 As shown, according to an embodiment of the present disclosure, the sealing bonding portion 330 also includes a sealing body 333, which covers at least one first sealing wall 331 and at least two second sealing walls 332 in an annular manner along the edge of the upper surface of the substrate 100, wherein the sealing body 333 includes a sealing gap 401, and the sealing gap 401 is recessed on the upper surface of the sealing body 333 corresponding to the gap 301 between adjacent first sealing walls 331 and second sealing walls 332.

[0071] The sealing body 333 is mainly used for direct contact bonding with the sealing bonding position of the cover plate structure 400 to enhance the bonding effect. The sealing body 333 directly covers the closed annular protrusion structure of the sealing bonding portion 330, that is, covers the entire first sealing wall 331 and the second sealing wall 332, and partially contacts the upper surface of the substrate 100, that is, Figure 10-11 The sealing body 333 implements a covering operation on the basis of the first sealing wall 331 and the second sealing wall 332, which can increase the overall height of the entire sealing bonding part 330, so that the sealing space 201 reaches a preset space width dimension, while also further strengthening the overall bonding strength of the sealing bonding part 330.

[0072] Due to the existence of the above-mentioned gap 301, the sealing body 333 after the covering operation simultaneously forms a sealing gap 401 corresponding to the gap 301. Due to the existence of the sealing gap 401 and the narrow and protruding setting of the upper end of the sealing body 333, based on the size of the above-mentioned first sealing wall 331 and the second sealing wall 332 and the gap 301, when the bonding process of the cover plate structure 400 and the sealing body 333 is carried out, the pressure at the upper end of the sealing body 333 corresponding to the second sealing wall 332 and the first sealing wall 331 is inconsistent, and the pressure at the corresponding first sealing wall 331 is greater, thereby ensuring that the bonding strength of the sealing bonding part 330 is better, thereby achieving better bonding sealing and stability, and improving the overall device structure quality.

[0073] like Figure 1-Figure 18 As shown, according to an embodiment of the present disclosure, the supporting bonding portion 340 includes a supporting body 341, which is disposed on the upper surface of the bottom electrode layer 320, wherein the supporting body 341 includes a supporting groove 501, which corresponds to the upper surface of the bottom electrode layer 320 and is recessed on the upper surface of the supporting body 341.

[0074] like Figure 1 and Figure 4-Figure 11 As shown, after the adhesion layer 310 and the bottom electrode layer 320 of the bottom electrode structure 300 are patterned, the two-layer structure forms regions of different sizes on the substrate 100, such as Figure 6 The support bonding part 340 is formed on the bottom electrode layer 320 located inside the sealing bonding part 330 on the resonance structure 200 .

[0075] The support body 341 has a plurality of support bodies, some of which are directly formed on one end of the bottom electrode layer 320 covering the resonant cavity of the resonant structure 200, and the other parts are directly formed on the pattern of the bottom electrode layer 320 spaced apart from the bottom electrode layer 320 covering the resonant cavity 201. Thus, by means of this patterned structure, the possibility of short circuit of the resonant structure can be effectively avoided, ensuring that the resonant function is maintained after bonding.

[0076] In addition, the support body 341 has a certain height design. Generally, the support body 341 has a support groove 501. The height difference h1 between the bottom surface of the support groove 501 and the upper surface of the substrate 100 should be equal to the height difference h2 between the end surface of the upper end of the sealing body 333 and the upper surface of the substrate 100. In this way, the parallel design between the cover plate 410 of the cover plate structure 400 and the substrate 100 can be achieved to prevent the cover plate 410 from being deformed and the sealed space 201 from being distorted, thereby further ensuring the resonance effect of the resonant structure 200.

[0077] like Figure 1-Figure 18As shown, according to an embodiment of the present disclosure, the resonant cavity 201 is recessed on the upper surface of the substrate 100, as shown in FIG. Figure 2-Figure 4 As shown, the design of the resonant cavity 201 can effectively ensure the resonance effect of the resonant structure 200. It should be noted that the resonant structure 200 of the embodiment of the present disclosure has multiple resonant cavities 201, that is, multiple resonant cavities 201 are recessed on the upper surface of the substrate 100 to enhance the resonance effect. After the bottom electrode structure 300 covers the multiple resonant cavities 201 separately or uniformly, the resonant structure 200 can provide more abundant device resonance functions.

[0078] like Figure 1-Figure 18 As shown, according to an embodiment of the present disclosure, the resonant structure 200 includes a piezoelectric layer 210, a top electrode layer 220 and a frequency modulation layer 230. The piezoelectric layer 210 is partially disposed on the upper surface of the substrate 100, and the other part is disposed on the upper surface of the bottom electrode layer 320, covering the resonant cavity 201; the top electrode layer 220 corresponds to the resonant cavity 201 and is disposed on the upper surface of the piezoelectric layer 210; and the frequency modulation layer 230 is disposed on the upper surface of the top electrode layer 220.

[0079] like Figure 9-10 As shown, after the piezoelectric layer 210 is patterned, part of the piezoelectric layer 210 can be disposed on the upper surface of the substrate 100, and the other part can be disposed on the upper surface of the bottom electrode layer 320, and can directly correspond to the resonant cavity 201 covering the B area. Among them, the top electrode layer 220 and the frequency modulation layer 230 can be disposed above the piezoelectric layer 210 in strict accordance with the shape and size of the resonant cavity 201, and protrude toward the cover structure 400 in the sealed space 201, so as to ensure the resonance effect of the resonant structure 200.

[0080] like Figure 1-Figure 18 As shown, according to an embodiment of the present disclosure, the piezoelectric layer 210 includes a plurality of first openings 202 and a plurality of second openings 203. The plurality of first openings 202 correspond to a plurality of first support bodies 341 of a plurality of support bonding parts, which penetrate the piezoelectric layer 210, and each first support body 341 of the plurality of first support bodies passes through the first opening 202 and is arranged on the upper surface of the bottom electrode layer 320; the plurality of second openings 203 correspond to a plurality of second support bodies 341 of a plurality of support bonding parts, which penetrate the piezoelectric layer 210, and each second support body 341 of the plurality of second support bodies passes through the second opening 203 and is arranged on the upper surface of the bottom electrode layer 320.

[0081] like Figure 9-10As shown, after the piezoelectric layer 210 is patterned, a first opening 202 and a second opening 203 can be formed on both sides of the piezoelectric layer 210. The first opening 202 is used to expose the upper surface of the bottom electrode layer 320 of the bottom electrode structure 300 covering the resonant cavity 201, and the second opening 203 is used to expose the upper surface of other bottom electrode layers 320 outside the bottom electrode layer 320 and inside the sealing bonding part 330. The support body 341 corresponding to the support bonding part 340 formed on the bottom electrode layer 320 exposed to the first opening 202 is the first support body 341, and the support body 341 corresponding to the support bonding part 340 formed on the bottom electrode layer 320 exposed to the second opening 203 is the second support body 341. In this way, the resonant structure 200 can be better separated, the short circuit of the resonant structure 200 can be avoided, and a better resonance effect can be maintained.

[0082] like Figure 1-Figure 18 As shown, according to an embodiment of the present disclosure, the cover plate structure 400 includes a cover plate 410, a cover plate bonding portion 420 and a first bonding layer 430. The cover plate bonding portion 420 corresponds to the sealing body 333 of the sealing bonding portion 330, and is provided along the edge of the lower surface of the cover plate 410, and is annularly sealed and convex, and is used to cooperate with the substrate 100 to form a sealed space 201; the first bonding layer 430 is provided on the top surface of the cover plate bonding portion 420, and is in contact with the upper surface of the sealing body 333.

[0083] like Figure 13-Figure 15 As shown, the cover plate 410 is the main structure of the cover plate structure 400, and is used to form the main bonding structure of the cover plate structure 400. The cover plate bonding part 420 is a closed annular protrusion, which is convexly arranged on the edge of the lower surface of the cover plate 410, and can be bonded and sealed with the sealing bonding part 330 to form a sealed space 201. In order to better seal the sealed space 201 and achieve a better sealing effect, a first bonding layer 430 is provided on the surface of the top end of the cover plate bonding part 420 for bonding, so as to contact and bond with the upper surface of the upper end of the sealing body 333 of the sealing bonding part 330, so as to achieve the best bonding and sealing effect in conjunction with the structural design of the upper end of the sealing body 333.

[0084] like Figure 1-Figure 18 As shown, according to an embodiment of the present disclosure, the cover plate structure 400 further includes a plurality of cover plate bonding pillars 440 and a plurality of second bonding layers 450. The plurality of cover plate bonding pillars 440 correspond to the support bodies 341 of the plurality of support bonding parts 340 and are disposed in the support grooves 501 of the support bodies 341; the plurality of second bonding layers 450 correspond to the top surfaces of the plurality of cover plate bonding pillars 440 and contact the bottom surfaces of the support grooves 501 of the plurality of support bonding parts 340.

[0085] The first bonding layer 430 and the second bonding layer 450 are the aforementioned embedded electrodes.

[0086] like Figure 13-Figure 15 As shown, the cover plate bonding column 440 is a separate columnar protrusion, corresponding one-to-one to the support body 341 supporting the bonding part 340, and protruding from the lower surface of the cover plate 410, and can achieve bonding and sealing together with the support body 341 to form a support structure for the sealed space 201. In order to better support the sealed space 201 and achieve a better supporting effect, a second bonding layer 450 is provided on the surface of the top end of the cover plate bonding column 440 for bonding, so as to be inserted into the support groove 501 of the support body 341, and contact and bond with the bottom surface of the support groove 501, so as to achieve the best bonding support effect in conjunction with the structural design of the support body 341, ensure the stability of the structure, the regular shape of the device, and improve the device structure quality.

[0087] like Figure 1-Figure 18 As shown, according to an embodiment of the present disclosure, the cover plate structure 400 further includes a plurality of electrode holes 402 and a plurality of back electrode layers 460. The plurality of electrode holes 402 correspond to the plurality of cover plate bonding pillars 440 and are penetrated by the plurality of cover plate bonding pillars 440; the plurality of back electrode layers 460 correspond to the plurality of electrode holes 402 and are disposed on the upper surface of the cover plate 410; wherein each back electrode layer 460 of the plurality of back electrode layers 460 passes through each electrode hole 402 of the plurality of electrode holes 402 and contacts the support body 341.

[0088] like Figure 14-18 As shown, the electrode hole 402 is used to provide a connection channel for the back electrode layer 460 to directly contact the support body 341. The back electrode layer 460 is used as an extraction electrode of the device structure.

[0089] like Figure 1-Figure 19 As shown, another aspect of the present disclosure provides a method for preparing the above-mentioned bulk acoustic wave filter, which includes steps S1901-S1903.

[0090] In step S1901, a resonant structure located in the middle of the substrate is formed on the substrate;

[0091] In step S1902, a bottom electrode structure is formed on the surface of the substrate and covers the resonant cavity of the resonant structure according to the resonant structure; and

[0092] In step S1903, the resonant structure is sealed in a sealed space between the cover structure and the substrate by bonding the cover structure and the bottom electrode structure.

[0093] like Figure 1-Figure 19 As shown, according to an embodiment of the present disclosure, in step S1902, according to the resonant structure, a bottom electrode structure located on the surface of the substrate and covering the resonant cavity of the resonant structure is formed, including: forming an adhesion layer covering the resonant cavity of the resonant structure on the upper surface of the substrate; and forming a bottom electrode layer on the upper surface of the adhesion layer.

[0094] Combination Figure 2-Figure 18 The content shown is for the above Fig.19 The corresponding Figure 1 The method for preparing the thin film bulk acoustic wave filter is described in detail by taking the following specific preparation steps S1-S14 as an example:

[0095] In step S1, Figure 2 As shown, a silicon dry etching process is used to form a silicon substrate 100 on the upper surface of the silicon substrate 100. Figure 1 The resonant cavity 201 of the thin film bulk acoustic wave filter is shown.

[0096] In step S2, if Figure 3 As shown, a sacrificial layer 510 is deposited in the resonant cavity 201 by chemical vapor deposition, and then the sacrificial layer outside the resonant cavity 201 is polished and removed by chemical mechanical polishing.

[0097] In step S3, if Figure 4 As shown, the adhesion layer 310 of the bottom electrode structure 300 is deposited by chemical vapor deposition process. The material of the adhesion layer 310 is generally aluminum nitride. The thickness of the adhesion layer 310 is about Afterwards, the bottom electrode layer 320 of the bottom electrode structure is deposited by a physical vapor deposition process. The material of the bottom electrode layer 320 is generally molybdenum. The thickness of the bottom electrode layer 320 is between.

[0098] In step S4, if Figure 5 As shown, 310 / 320 of the bottom electrode structure 300 is etched by a dry etching process to achieve structural patterning, forming a sealing area corresponding to the sealing bonding part 330, a functional area B and a supporting electrode area of ​​the supporting bonding part 340, as shown in FIG. Figure 6 As shown, according to the top plan view of the bottom electrode structure 300 after etching, the pattern of 310 / 320 of the bottom electrode structure 300 in the sealing area after etching needs to ensure that the raised portion of the edge of the upper surface of the substrate 100 (corresponding to the sealing bonding portion 330) is continuous and uninterrupted. Figure 7 As shown, after patterning, the thickness dimension d of the first sealing wall 331 of the sealing bonding part 330 is greater than or equal to 1μm, the thickness dimension b of the second sealing wall 332 is greater than or equal to 1μm, the width dimension c of the gap 301 therebetween is greater than or equal to 1um, and b is greater than or equal to d.

[0099] In step S5, Figure 8 As shown, by chemical vapor deposition process Figure 7 The piezoelectric layer 210 is deposited on the surface of the device structure shown in the figure. The material of the piezoelectric layer 210 is generally aluminum nitride. The thickness of the piezoelectric layer 210 is about -2um;

[0100] In step S6, Fig. 9 As shown, a top electrode layer 220 and a frequency modulation layer 230 are prepared on the piezoelectric layer 210 by physical vapor deposition and chemical vapor deposition processes. Afterwards, the two are left only above the resonant cavity 201 by a patterning process; the material of the top electrode layer 220 is generally metal molybdenum, and the thickness of the top electrode layer 220 is about The material of the frequency modulation layer 230 is generally aluminum nitride.

[0101] In step S7, Fig.10 As shown, the first sealing wall 331 and the second sealing wall 332 of the sealing bonding part 330 are formed by a dry etching process or a wet etching process, wherein all the piezoelectric layers 210 from the outside of the bottom electrode structure 330 to the edge of the substrate 100 are completely removed.

[0102] In step S8, Fig.11 As shown, a sealing body 333 of the sealing bonding part 330 and a supporting body 341 supporting the bonding part 340 are respectively prepared by a physical vapor deposition process and an evaporation process. The materials of the sealing body 333 and the supporting body 341 are generally gold, and the thicknesses of the two are respectively controlled between 0.5um and 2um; the horizontal thickness dimension k of the sealing body 333 is greater than the overall thickness 2b+2c+d of the first sealing wall 331, the second sealing wall 332 and the gap 301, so as to achieve overall coverage of the two sealing walls, as shown in FIG. Fig.12 As shown, the dimension a of the excess side of the sealing body 333 is greater than or equal to 3 um.

[0103] In step S9, if Fig.13 As shown, a cover bonding portion 420 and a plurality of cover bonding columns 440 are prepared on a protective silicon substrate 410 (i.e., a cover 410, which is the same silicon wafer as the substrate 100) by a silicon dry etching process. The overall heights of the cover bonding portion 420 and the plurality of cover bonding columns 440 are generally the same, and are mostly controlled between 2μm-10μm.

[0104] In step S10, Fig.14 As shown, an electrode hole 402 is prepared on the cover substrate bonding column 440 by a deep silicon etching process.

[0105] In step S11, Fig.15 As shown, a layer of bonding electrode, namely a first bonding layer 430 and a second bonding layer 450, are prepared on the cover bonding part 420 and the plurality of cover bonding pillars 440 respectively by physical vapor deposition process and evaporation process. The material of the first bonding layer 430 and the second bonding layer 450 is generally gold, and the thickness is controlled between 0.5um and 2um.

[0106] In step S12, Fig.16 As shown, the prepared cover structure 400 and the substrate 100 having the bottom electrode structure 300 and the resonant structure 200 are bonded to each other through a wafer-level gold-gold hot-pressing bonding process to achieve bonding and sealing between the two.

[0107] In step S13, Fig.17 As shown, the back side of the protective cover plate 410 is thinned by mechanical grinding, so that the electrode hole 402 penetrates the cover plate 410 .

[0108] In step S14, Fig.18 As shown, a layer of external electrode (i.e., back electrode layer 460) is prepared on the back surface of electrode hole 402 and protective cover 410 through physical vapor deposition process and electroplating process. The material of back electrode layer 460 can be copper or gold to realize the interconnection of the device with the outside through protective cover 410.

[0109] Obviously, based on the detailed description of the above steps S1-S14, the above-mentioned embodiment of the present disclosure is further reflected. Figure 1 The device structure shown, compared with the structural form of the prior art in which the bottom electrode is set based on the etched groove or through hole on the substrate 100, cancels the groove design on the micro-cap structure, simplifies the number of micro-cap wafer processing layers and processes, that is, in the formation process of the bottom electrode structure, the groove etching of the substrate and other processes will be effectively avoided, which greatly simplifies the preparation process, thereby reducing the preparation cost, and through the patterning of the bottom electrode structure, the bonding electrode in the sealing area is directly in contact with the silicon substrate, isolating the possibility of corrosive liquids such as hydrofluoric acid corroding the aluminum nitride of the adhesion layer in the sealing area to form microscopic channels, thereby improving the device reliability, better maintaining the device function, and further improving the device performance from a structural point of view, thereby improving the device structure quality.

[0110] Therefore, compared with the structural design in the prior art in which the bottom electrode structure is recessed in the groove of the substrate, by directly forming the bottom electrode structure on the upper surface of the substrate, the processes such as trench etching of the substrate are eliminated, the number of micro-cap wafer processing layers and the processing steps are simplified, the cost is greatly reduced, and at the same time the device performance and device quality of the bulk acoustic wave filter can be guaranteed.

[0111] So far, the embodiments of the present disclosure have been described in detail with reference to the accompanying drawings.

[0112] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A bulk acoustic wave filter, wherein: include: substrate, A resonant structure is arranged in the middle of the substrate; A bottom electrode structure, disposed on the surface of the substrate and covering the resonant cavity of the resonant structure; A cover plate structure is bonded to the bottom electrode structure to seal the resonant structure in a sealed space between the cover plate structure and the substrate. Wherein, the bottom electrode structure comprises: an adhesive layer, disposed on the upper surface of the substrate and covering the resonant cavity; A bottom electrode layer, disposed on the upper surface of the adhesion layer; Wherein, the adhesion layer and the bottom electrode layer constitute a bottom electrode pattern structure, Wherein, the bottom electrode structure further includes: A sealing bonding portion is provided along the edge of the upper surface of the substrate in an annular sealing manner to form the sealing space; A plurality of supporting bonding parts surround the resonant structure and are distributed and protruded on the upper surface of the substrate to support the sealed space. Wherein, the sealing bonding part comprises: at least one first sealing wall; At least two second sealing walls sandwiching the at least one first sealing wall; Wherein, at least two second sealing walls and the at least one first sealing wall are closed annular structures protruding along the edge of the upper surface of the substrate, the thickness of the second sealing wall is greater than or equal to the thickness of the first sealing wall, there is a gap between adjacent first sealing walls and second sealing walls, and the sealing bonding portion further includes: A sealing body, which is arranged along the edge of the upper surface of the substrate and covers the at least one first sealing wall and the at least two second sealing walls in an annular manner, wherein the sealing body comprises: A sealing gap is recessed on the upper surface of the sealing body corresponding to the gap between the adjacent first sealing walls and the second sealing walls.

2. The bulk acoustic wave filter according to claim 1, wherein The supporting bonding portion comprises: A support body is disposed on the upper surface of the bottom electrode layer, wherein the support body comprises: The supporting groove corresponds to the upper surface of the bottom electrode layer and is concavely arranged on the upper surface of the supporting body.

3. The bulk acoustic wave filter according to claim 1, wherein The resonant structure comprises: A piezoelectric layer, part of which is disposed on the upper surface of the substrate, and the other part of which is disposed on the upper surface of the bottom electrode layer, covering the resonant cavity; A top electrode layer, corresponding to the resonant cavity, is disposed on the upper surface of the piezoelectric layer; The frequency modulation layer is arranged on the upper surface of the top electrode layer.

4. The bulk acoustic wave filter according to claim 3, wherein: The piezoelectric layer comprises: A plurality of first openings, wherein a plurality of first support bodies corresponding to the plurality of support bonding portions are arranged through the piezoelectric layer, and each of the plurality of first support bodies is arranged on the upper surface of the bottom electrode layer through the first opening; A plurality of second openings, corresponding to a plurality of second support bodies of the plurality of support bonding portions, are provided through the piezoelectric layer, and each of the plurality of second support bodies is provided on the upper surface of the bottom electrode layer through the second opening.

5. The bulk acoustic wave filter according to claim 1, wherein The resonant cavity is concavely arranged on the upper surface of the substrate.

6. The bulk acoustic wave filter according to claim 1, wherein The cover plate structure comprises: Cover plate, A cover plate bonding part, corresponding to the sealing body of the sealing bonding part, is provided along the edge of the lower surface of the cover plate, and is annularly sealed and convex, and is used to cooperate with the substrate to form the sealed space; The first bonding layer is arranged on the top surface of the cover plate bonding portion and contacts the upper surface of the sealing body.

7. The bulk acoustic wave filter according to claim 2, wherein: The cover plate structure also includes: A plurality of cover plate bonding pillars, corresponding to the supporting bodies of the plurality of supporting bonding parts and arranged in the supporting grooves of the supporting bodies; A plurality of second bonding layers are correspondingly arranged on the top end surfaces of the plurality of cover plate bonding pillars and contact the bottom surfaces of the supporting grooves of the plurality of supporting bonding parts.

8. The bulk acoustic wave filter according to claim 7, wherein: The cover plate structure also includes: A plurality of electrode holes, corresponding to the plurality of cover plate bonding pillars and penetrating the plurality of cover plate bonding pillars; A plurality of back electrode layers, corresponding to the plurality of electrode holes, and disposed on the upper surface of the cover plate; Wherein, each of the plurality of back electrode layers passes through each of the plurality of electrode holes and contacts the support body.

9. A method for preparing a bulk acoustic wave filter according to any one of claims 1 to 8, wherein: include: forming a resonant structure on a substrate and located in the middle of the substrate; According to the resonant structure, a bottom electrode structure is formed which is located on the surface of the substrate and covers the resonant cavity of the resonant structure; as well as The resonant structure is sealed in a sealed space between the cover plate structure and the substrate by bonding the cover plate structure and the bottom electrode structure.

10. The preparation method according to claim 9, wherein: In the bottom electrode structure of the resonant cavity formed on the surface of the substrate and covering the resonant structure according to the resonant structure, the bottom electrode structure includes: forming an adhesive layer covering the resonant cavity of the resonant structure on the upper surface of the substrate; A bottom electrode layer is formed on an upper surface of the adhesion layer.

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