Method for manufacturing thin film bulk acoustic wave resonator

Abstract

The present invention provides a method for manufacturing a thin film bulk acoustic wave resonator. In the manufacturing method, a bulk acoustic wave film and a support structure are sequentially formed on a first substrate, the support structure includes a main support wall, an isolation wall and an auxiliary support column, the isolation wall is arranged in the main support wall, the auxiliary support column is arranged in the isolation wall, and after bonding the second substrate and removing the first substrate, the auxiliary support column and the isolation wall are removed through a release window located within the range defined by the isolation wall. The auxiliary support column helps to provide effective support in the process of film layer transfer and other support structures, and the isolation wall formed between the main support wall and the auxiliary support column can protect the main support wall from being eroded during the process of removing the auxiliary isolation wall, thereby improving the reliability of the cavity located within the range defined by the main support wall.

Description

Technical Field

[0001] The invention relates to the field of filters, and in particular to a method for manufacturing a thin film bulk acoustic wave resonator. Background Art

[0002] With the continuous development of wireless communication technology, in order to meet the multifunctional requirements of various wireless communication terminals, terminal equipment needs to be able to use different carrier spectra to transmit data. At the same time, in order to support sufficient data transmission rate within a limited bandwidth, strict performance requirements are also put forward for the RF system. RF filter is an important part of the RF system, which can filter out interference and noise outside the communication spectrum to meet the signal-to-noise ratio requirements of the RF system and communication protocol. Taking mobile phones as an example, since each frequency band requires a corresponding filter, dozens of filters may need to be set in a mobile phone.

[0003] Filters usually include inductors, capacitors, and resonators. In piezoelectric-based resonators, acoustic resonance modes are generated in piezoelectric materials, and acoustic waves are converted into electric waves for use. Bulk acoustic wave (BAW) resonators are a type of piezoelectric resonator. By cascading different BAW resonators, BAW filters that meet different performance requirements can be made. Film bulk acoustic wave resonator (FBAR) is a type of BAW resonator, in which a BAW film is mounted on a cavity formed on a substrate as a reflective element. The BAW film usually includes a piezoelectric film disposed between two electrodes. The acoustic wave achieves resonance across the BAW film, and the resonant frequency is mainly determined by the material of the BAW film. Film BAW resonators have the advantages of a high quality factor Q value, can be integrated on an IC chip, and are compatible with CMOS processes, and have achieved rapid development in recent years.

[0004] Currently, one method for forming a thin film bulk acoustic wave resonator is to first etch a pit on a substrate and fill the pit with a sacrificial layer material, then form a bulk acoustic wave film on the sacrificial layer, and subsequently etch a window from the bulk acoustic wave film to remove the sacrificial layer from the window. In this method, since a bulk acoustic wave film is formed on the sacrificial layer, the roughness of the underlying layer has an important influence on the performance of the bulk acoustic wave film, so the roughness needs to be specially controlled, which increases the complexity of the process. In addition, it is difficult to obtain high-quality single crystal piezoelectric films with this method, which is not conducive to improving the performance of thin film bulk acoustic wave resonators.

[0005] Another method for forming a thin film bulk acoustic wave resonator is to use a prepared substrate to form a bulk acoustic wave film and a support structure on the bulk acoustic wave film without using a sacrificial layer material, and then bond it to another substrate through the support structure, then remove the prepared substrate, and separate the electrodes to form a resonant structure on the cavity. In order to improve the strength of the bulk acoustic wave film, the support structure includes auxiliary support columns set within the cavity in addition to the main support wall that defines the cavity range. The auxiliary support columns are removed after the resonant structure is made. However, the process of removing the auxiliary support columns is likely to cause erosion to the main support wall of the support structure, resulting in unstable performance of the resonant structure. Summary of the invention

[0006] Based on the problems existing in the existing process, the present invention provides a method for manufacturing a thin film bulk acoustic wave resonator to improve the stability of the thin film bulk acoustic wave resonator, and the manufacturing process is relatively easy.

[0007] The method for manufacturing a bulk acoustic wave resonator provided by the present invention comprises the following steps:

[0008] A first substrate is provided; an isolation layer and a bulk acoustic wave film located on the isolation layer are formed on the first substrate; a support structure is formed on the bulk acoustic wave film, the support structure comprising a main support wall, an isolation wall and an auxiliary support column which are arranged in sequence from the outside to the inside on the upper surface of the bulk acoustic wave film, the main support wall and the isolation wall are both annular structures, the isolation wall is arranged inside the main support wall, and the auxiliary support column is arranged inside the isolation wall; the side of the first substrate formed with the support structure is bonded to a second substrate, and the first substrate is removed; a release window is formed in the bulk acoustic wave film, the release window connects the space defined by the isolation wall with the outside; and the auxiliary support column and the isolation wall are removed by using the release window.

[0009] In the method for manufacturing a thin film bulk acoustic wave resonator provided by the present invention, the auxiliary support columns help to provide effective support during film layer transfer and other processes performed above the support structure, and the isolation wall formed between the main support wall and the auxiliary support columns can effectively protect the main support wall during the process of removing the auxiliary isolation wall, reducing or avoiding the risk of erosion of the main support wall, thereby facilitating improving the reliability of the subsequent cavity within the limited range of the main support wall and enhancing the resonance performance of the formed thin film bulk acoustic wave resonator. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a schematic flow chart of a method for manufacturing a thin film bulk acoustic resonator according to an embodiment of the present invention;

[0011] Figures 2 to 8 It is a cross-sectional schematic diagram of each step of a method for manufacturing a thin film bulk acoustic wave resonator according to an embodiment of the present invention.

[0012] Description of reference numerals:

[0013] 100-first substrate; 200-second substrate; 110-isolation layer; 120-bulk acoustic wave film; 121-first electrode layer; 122-piezoelectric layer; 123-second electrode layer; 130-support structure; 131-main support wall; 132-isolation wall; 133-auxiliary support column; 123a-edge trimming area; 120a-release window; 140-cavity. DETAILED DESCRIPTION

[0014] The following is a further detailed description of the method for making the bulk acoustic wave resonator of the present invention in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will become clearer. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise proportions. They are only used to conveniently and clearly assist in explaining the embodiments of the present invention. The embodiments of the present invention should not be considered to be limited to the specific shapes of the areas shown in the figures. For the sake of clarity, in all the drawings used to assist in explaining the embodiments of the present invention, the same components are in principle marked with the same reference numerals, and repeated descriptions thereof are omitted.

[0015] It should be noted that the terms "first", "second", etc., hereinafter are used to distinguish between similar elements, and are not necessarily used to describe a specific order or time sequence. It is to be understood that, where appropriate, these terms used in this way are interchangeable, for example, so that the embodiments of the present invention described herein can be operated in a different order than that described or shown herein. Similarly, if the method described herein includes a series of steps, and the order of these steps presented herein is not necessarily the only order in which these steps can be performed, and some of the steps described may be omitted and / or some other steps not described herein may be added to the method.

[0016] Figure 1 FIG. 1 is a flow chart of a method for manufacturing a thin film bulk acoustic wave resonator according to an embodiment of the present invention. Figure 1 The method for making a bulk acoustic wave resonator comprises the following steps:

[0017] S1: providing a first substrate;

[0018] S2: forming an isolation layer and a bulk acoustic wave thin film on the isolation layer on the first substrate;

[0019] S3: forming a support structure on the BAW film, the support structure comprising a main support wall, a separation wall and an auxiliary support column which are sequentially arranged on the upper surface of the BAW film from the outside to the inside, the main support wall and the separation wall are both annular structures, the separation wall is arranged inside the main support wall, and the auxiliary support column is arranged inside the separation wall;

[0020] S4: bonding the side of the first substrate on which the support structure is formed to a second substrate, and removing the first substrate;

[0021] S5: forming a release window in the bulk acoustic wave film, wherein the release window enables the space defined by the isolation wall to communicate with the outside world;

[0022] S6: Using the release window to remove the auxiliary support column and the isolation wall.

[0023] Figures 2 to 8 FIG. 1 is a cross-sectional schematic diagram of each step of a method for manufacturing a thin film bulk acoustic wave resonator according to an embodiment of the present invention. Figures 2 to 8 A method for manufacturing a thin film bulk acoustic wave resonator according to an embodiment of the present invention is further described.

[0024] First, step S1 is performed to provide a first substrate 100. In this embodiment, the first substrate 100 is used as a base to subsequently manufacture a BAW film and a support structure of a BAW resonator.

[0025] The first substrate 100 can be selected from the preparation substrate and support substrate commonly used in the art. Specifically, the material of the first substrate 100 can be any suitable base material well known to those skilled in the art, for example, it can be at least one of the following materials: silicon (Si), germanium (Ge), silicon germanium (SiGe), carbon silicon (SiC), carbon germanium silicon (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP) or other III / V compound semiconductors, including multilayer structures composed of these semiconductors, or silicon on insulator (SOI), stacked silicon on insulator (SSOI), stacked silicon germanium on insulator (S-SiGeOI), silicon germanium on insulator (SiGeOI) and germanium on insulator (GeOI), or it can also be double-side polished silicon wafers (Double Side Polished Wafers, DSP), or ceramic substrates such as aluminum oxide, quartz or glass substrates, etc. In this embodiment, the first substrate 100 is, for example, a P-type high-resistance single-crystal silicon wafer with a (100) crystal plane on the upper surface. Of course, the first substrate 100 may also include other materials known in the art.

[0026] Figure 2 FIG. 1 is a cross-sectional schematic diagram of a bulk acoustic wave thin film formed by a method for manufacturing a thin film bulk acoustic wave resonator according to an embodiment of the present invention. Figure 1 and Figure 2 , performing step S2 to form an isolation layer 110 and a bulk acoustic wave thin film 120 located on the isolation layer 110 on the first substrate 100 .

[0027] The isolation layer 110 can be used as a buffer material for forming a bulk acoustic wave film 120 on the first substrate 100. The isolation layer 110 can be formed on the first substrate 100 by a suitable method (such as chemical vapor deposition, physical vapor deposition, atomic layer deposition, coating or thermal oxidation method, etc.). The material of the isolation layer 110 can be any suitable material that can be easily covered on the first substrate 100 and is not easy to react with the subsequent bulk acoustic wave film 120, such as a dielectric material, etc. The dielectric material includes but is not limited to at least one of silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, aluminum nitride, titanium oxide, titanium nitride, fluorocarbons, carbon-doped silicon oxide, silicon carbonitride and the like. In other embodiments, the isolation layer 110 can be any suitable material that can be easily covered on the first substrate 100 and is not easy to react with the subsequent bulk acoustic wave film, such as amorphous carbon, photocurable adhesive, hot melt adhesive or laser ablation adhesive layer (such as polymer material), etc. On the one hand, the isolation layer 110 can help to avoid the influence of defects on the surface of the first substrate 100 on the preparation of the bulk acoustic wave film 120, thereby improving the performance and reliability of the device. On the other hand, it can make it possible to remove the first substrate 100 through a back thinning process (such as chemical mechanical planarization, etc.) and control the stop point in the removal process of the first substrate 100 to prevent damage to the subsequently formed bulk acoustic wave film 120. The thickness of the isolation layer 110 is about 0.1μm to 2μm, and can be selected to be less than 1μm.

[0028] The isolation layer 110 may include an etch stop layer (not shown) located on the upper layer and a sacrificial material layer (not shown) located between the etch stop layer and the first substrate 100. The thickness of the etch stop layer in the isolation layer 110 is relatively thin (e.g., ), the etch stop layer, the sacrificial material layer and the subsequently formed bulk acoustic wave film 120 (specifically referring to the electrode layer closer to the first substrate 100) all have a high etching selectivity, thereby being able to serve as a process stop point for the subsequent separation of the bulk acoustic wave film 120 and the first substrate 100, thereby avoiding unnecessary damage to the bulk acoustic wave film 120 when removing the first substrate 100. The etch stop layer is, for example, silicon oxide, silicon nitride or silicon oxynitride; the sacrificial material layer in the isolation layer 110 can be any suitable material that can easily separate the first substrate 100 and the bulk acoustic wave film 120, so as to reduce the difficulty of the subsequent process of removing the first substrate 100.

[0029] Reference Figure 2In this embodiment, the bulk acoustic wave film 120 includes a first electrode layer 121, a piezoelectric layer 122 and a second electrode layer 123 which are sequentially stacked on the isolation layer 10. The shapes of the first electrode layer 121, the piezoelectric layer 122 and the second electrode layer 123 may be the same or different, and the areas of the first electrode layer 121, the piezoelectric layer 122 and the second electrode layer 123 may be the same or different. After the first substrate 100 and the second substrate 200 are subsequently bonded, a resonant structure may be obtained by a patterning process, and the patterned first electrode layer 121 and the second electrode layer 123 serve as upper and lower electrodes of the resonant structure, respectively. In another embodiment of the present invention, the bulk acoustic wave film 120 may also include other film layers in addition to the first electrode layer 121, the piezoelectric layer 122 and the second electrode layer 123, which may be reasonably arranged according to the actual device and are not specifically limited here.

[0030] The first electrode layer 121 and the second electrode layer 123 may use any suitable conductive material or semiconductor material known to those skilled in the art, wherein the conductive material may be a metal material having conductive properties, for example, made of one of metals such as molybdenum (Mo), aluminum (Al), copper (Cu), tungsten (W), tantalum (Ta), platinum (Pt), ruthenium (Ru), rhodium (Rh), iridium (Ir), chromium (Cr), titanium (Ti), silver (Ag), gold (Au), osmium (Os), rhenium (Re), palladium (Pd), tin (Sn), or a stack of the above metals, and the semiconductor material may be, for example, Si, Ge, SiGe, SiC, SiGeC, etc. The first electrode layer 121 and the second electrode layer 123 may be formed by physical vapor deposition or chemical vapor deposition methods such as magnetron sputtering and evaporation. The first electrode layer 121 and the second electrode layer 123 are preferably made of the same material, but different conductive materials may be selected according to actual requirements in specific implementation. The piezoelectric layer 122 may also be referred to as a piezoelectric resonance layer or a piezoelectric resonance structure, and may be made of one or more piezoelectric materials such as quartz, aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), lithium niobium oxide (LiNbO3), lithium tantalum oxide (LiTaO3), etc., and the piezoelectric layer 122 may also be doped with rare earth elements. In this embodiment, the material of the first electrode layer 121 and the second electrode layer 123 is, for example, molybdenum, and the material of the piezoelectric layer 122 is, for example, aluminum nitride. The thickness of the first electrode layer 121 and the second electrode layer 123 is approximately in the range of 100nm to 200nm. The thickness of the piezoelectric layer 122 is in the range of 1μm to 3μm, and can be specifically set according to the target resonant frequency. For example, the thickness of the piezoelectric layer 122 can be set to 1 / 2 of the resonant wavelength. Molybdenum can be deposited using a PVD (physical vapor deposition) process or a magnetron sputtering process, and aluminum nitride can be deposited using a PVD (physical vapor deposition) process or MOCVD (metal organic chemical vapor deposition).

[0031] Figure 3 It is a cross-sectional schematic diagram after a support structure is formed by using a method for manufacturing a thin film bulk acoustic wave resonator according to an embodiment of the present invention. Figure 4 yes Figure 3 Schematic diagram of the top view of the support structure. Figure 3 and Figure 4 , step S3 is performed to form a support structure 130 on the bulk acoustic wave film 120, wherein the support structure 130 includes a main support wall 131, a separation wall 132 and an auxiliary support column 133 which are sequentially arranged on the upper surface of the bulk acoustic wave film 120 from the outside to the inside, wherein the main support wall 131 and the separation wall 132 are both annular structures, the separation wall 132 is arranged in the main support wall 131, and the auxiliary support column 133 is arranged in the separation wall 132. The support structure 130 can be obtained by depositing a support material on the second electrode layer 123 and using a patterning process. The support material can be any suitable material that is not easy to react with the bulk acoustic wave film, and the optional support material includes but is not limited to silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, aluminum nitride, titanium oxide, titanium nitride, amorphous carbon, tetraethyl orthosilicate, etc. The support material can also include other materials known in the art, such as dry film, etc. The support material can also include a superimposed layer of two or more materials. The supporting material can be selected from at least one of the materials with greater mechanical strength such as silicon oxide, silicon nitride, silicon oxynitride, etc. The supporting structure 130 formed thereby is conducive to forming a supporting column with sufficient supporting force, thereby increasing the stability of the device structure and preventing the bulk acoustic wave film from being deformed or breaking due to the pressure difference inside and outside the cavity in subsequent processes. On the other hand, it can also prevent leakage between the formed bulk acoustic wave film and the subsequent second substrate, and improve the adhesion between the subsequent second substrate and the bulk acoustic wave film, thereby improving device performance and reliability.

[0032] By forming the support structure 130, the scope of the resonant air cavity (hereinafter referred to as the cavity) to be formed subsequently can be limited on the first substrate 100, so that there is no need to use a sacrificial layer to construct the scope of the cavity, and the process is simple and easy to control. In this embodiment, the support structure 130 includes a main support wall 131 arranged at the outermost periphery, and the main support wall 131 is formed on the bulk acoustic wave film 120, and is used to define the position and scope of the cavity of the bulk acoustic wave resonator. The shape of the main support wall 131 along the cross section parallel to the first substrate 100 can be rectangular, circular, pentagonal, hexagonal, etc. In addition, an isolation wall 132 and an auxiliary support column 133 are also provided within the scope defined by the main support wall 131, which has the function of further strengthening the support, and helps to improve the reliability of the film layer, avoid collapse, and reduce the difficulty of process control in the process of bonding the first substrate 100 and the second substrate 200 to realize the film layer transfer of the bulk acoustic wave film 120 and in the process of making the resonant structure until packaging. The auxiliary support column 133 is arranged within the range defined by the isolation wall 132. There can be more than one auxiliary support column 133. At least one auxiliary support column 133 can be arranged as a solid columnar structure. For example, more than two columnar auxiliary support columns 133 can be arranged to be evenly distributed within the range defined by the isolation wall 132 for auxiliary support. At least one auxiliary support column 133 can also be arranged as a closed or non-closed annular wall structure, and the annular wall structure is spaced apart from the isolation wall 132 to provide auxiliary support within the range defined by the isolation wall 132. The auxiliary support column 133 with a columnar structure is mainly used as an example for explanation. There are gaps between adjacent auxiliary support columns 133, between each auxiliary support column 133 and the isolation wall 132, and between the isolation wall 132 and the main support wall 131. Combined with the supporting function of the main support wall 131 and the isolation wall 132, a stable support can be provided for the upper membrane layer. The cross-sectional shape of each auxiliary support column 133 parallel to the first substrate 100 can be one or a combination of two or more of the following patterns: circular, elliptical, quadrilateral, pentagonal, hexagonal, etc. When at least two auxiliary support columns 133 are formed, the shapes of these auxiliary support columns 133 can be the same or different. Also, the dimensions of these auxiliary support columns 133 in the same direction can be the same or different. In this embodiment, the longitudinal cross-sectional shape of the auxiliary support column 133 is a rectangle (such as Figure 3 As shown), that is, the upper and lower widths are consistent. However, in specific implementation, the longitudinal cross-sectional shape of the auxiliary support column 133 can be other shapes such as a regular trapezoid or an inverted trapezoid, which can also achieve the purpose of the present invention. Optionally, two or more auxiliary support columns 133 of the same shape and uniform distribution are formed within the range defined by the isolation wall 132, so that relatively uniform support can be provided in the subsequent process of manufacturing the resonant structure after removing the first substrate 100.

[0033] The isolation wall 132 is located between the main support wall 131 and the auxiliary support column 133 and is formed into a ring shape. When the auxiliary support column 133 is removed later, the release window of the etching gas or etching liquid is set within the range defined by the isolation wall 132, so that the etching gas or etching liquid can mainly etch the auxiliary support column 133 and the isolation wall 132 within the range of the isolation wall 132. Due to the obstruction of the isolation wall 132, the main support wall 131 is isolated from the etching atmosphere or etching liquid by the isolation wall 132, which can greatly reduce the possibility of being corroded (such as lateral etching). Since the main support wall 131 is basically not damaged by corrosion, it helps to improve the stability of the cavity (as the resonant cavity of the bulk acoustic wave resonator) defined by the main support wall 131 later, thereby improving the performance of the bulk acoustic wave resonator.

[0034] The main support wall 131, the isolation wall 132 and the auxiliary support column 133 of the support structure 130 can be set to the same height to achieve a common support effect. In this embodiment, the main support wall 131, the isolation wall 132 and the auxiliary support column 133 in the support structure 130 are basically the same height, about 3μm. However, it is not limited to this. According to different material selections and process errors, the support structure 130 can be a material with a certain elasticity. When playing a supporting role, according to the different distances between the upper and lower contact interfaces, the actual heights of the main support wall 131, the isolation wall 132 and the auxiliary support column 133 can be different. In addition, since the isolation wall 132 is mainly used to protect the main support wall 131 during the removal of the auxiliary support column, its height can also be set lower than the height of the main support wall 131 and the auxiliary support column 133. The spacing and size of the main support wall 131, the isolation wall 132 and the auxiliary support column 133 can also be designed according to the specific process and structure. For example, the thickness of the isolation wall 132 can be specifically set according to the number of auxiliary support columns and the difficulty of etching to remove the auxiliary support columns. Optionally, along the thickness direction of the main support wall 131, the size of the auxiliary support columns 133 and the isolation wall 132 can be set to be smaller than the thickness of the main support wall 131, for example, set to less than 1 / 3 of the thickness of the main support wall 131, so as to facilitate the subsequent rapid removal of the auxiliary support columns 133 and the isolation wall 132, and reduce or avoid the impact on the main support wall 131 during the process of removing the auxiliary support columns 133 and the isolation wall 132. If necessary, more than one circle of the isolation wall 132 can be provided. For example, in another embodiment, in the support structure on the bulk acoustic wave film 120, two or three circles of the isolation wall 132 can be nested between the main support wall 131 and the auxiliary support columns 133. In this embodiment, the longitudinal cross-sectional shape of the main support wall 131 and the isolation wall 132 in the thickness direction is a rectangle (such as Figure 3However, in specific implementation, the longitudinal cross-section shape of the main support wall 131 and the isolation wall 132 in the thickness direction can be other shapes such as a regular trapezoid or an inverted trapezoid, which can also achieve the purpose of the present invention.

[0035] By using the above-mentioned support structure 130, in the subsequent etching process of removing the auxiliary support pillars 133, the inner surface of the isolation wall 132 facing the auxiliary support pillars 133 will also be etched. In order to completely remove the auxiliary support pillars 133 during this etching process and minimize the impact on the main support wall 131, the width of the isolation wall 132 can be slightly greater than or equal to the dimension of the auxiliary support pillars 133 in the width direction of the isolation wall 132. Here, the width direction of the isolation wall 132 refers to the direction from the outside of the isolation wall 132 to the center of the area defined by it in a plane parallel to the first substrate 100. Since the isolation wall 132 is subjected to single-sided etching, while the auxiliary support pillars 133 are subjected to etching in all directions, by using the above-mentioned width relationship, it can be basically ensured that the process of removing the auxiliary support pillars 133 does not affect the main support wall 131. In addition, optionally, the isolation wall 132 can be completely removed in the process after the auxiliary support column 133 is removed by controlling the etching time, while the main support wall 131 and the cavity range defined by it are basically not affected, thereby helping to improve the reliability of the resonant cavity and enhance the performance of the BAW resonator. According to the design requirements of the resonant structure of the BAW resonator, the resonant region of the BAW film 120 can have a circular, elliptical or polygonal shape (parallel to the cross section of the first substrate 100), and the shape of the support structure 130 can also be designed accordingly to save space. Figure 4 FIG. 1 is a plan view of a support structure in a method for manufacturing a thin film bulk acoustic wave resonator according to an embodiment of the present invention. Figure 4 For example, the main support wall 131 may have a planar shape similar to that of the resonant structure to be formed subsequently (e.g., a pentagon, hexagon, or heptagon, etc.), where "similar" means that the planar shape of the main support wall 131 and the planar shape of the resonant structure are similar polygons or similar circles, and the corresponding sides are proportional. Specifically, when setting the isolation wall 132, the shape of the main support wall 131 can be adapted, that is, the isolation wall 132 is set to the same planar shape that coincides with the center of the main support wall 131 and is reduced, thereby forming a gap with a uniform width between the main support wall 131 and the isolation wall 132 to save space. The auxiliary support column 133 is set in the isolation wall 132. Figure 4 As shown, in this embodiment, in a plane parallel to the surface of the first substrate 100, the planar shapes of the main support wall 131 and the isolation wall 132 can both be pentagons.

[0036] In order to reduce or avoid the impact of the subsequent etching process of removing the isolation wall 132 and the auxiliary support column 133 on the main support wall 131, in another embodiment of the present invention, the main support wall 131, the isolation wall 132 and the auxiliary support column 133 in the support structure 130 can also be made of different materials. For example, if wet etching is subsequently used to remove the auxiliary support column 133, the wet etching process preferably has a higher etching rate for the auxiliary support column 133 and the isolation wall than for the main support wall 131. In addition, according to design requirements, the isolation wall 132 and the auxiliary support column 133 can also be made of different materials, so that when wet etching is used to remove the auxiliary support column 133, the etching rate of the auxiliary support column 133 can be greater than the etching rate of the isolation wall 132, so as to avoid the isolation wall 132 being etched through and the etching liquid corroding the main support wall 131.

[0037] As examples, several optional embodiments of forming the support structure 130 are described below.

[0038] In an optional first embodiment, forming the support structure 130 on the bulk acoustic wave film 120 includes the following steps: first, forming a support layer of a preset thickness on the bulk acoustic wave film 120. Specifically, a silicon dioxide film layer of about 2 μm to 5 μm can be deposited on the second electrode layer 123 of the bulk acoustic wave film 120 by chemical vapor deposition as a support layer, and then the surface of the support layer is flattened by a CMP process. Then, the support layer is etched by a patterning process to form the support structure 130. The patterning process may include processes such as exposure, development, etching, and demolding.

[0039] In the first embodiment described above, the main support wall 131 , the isolation wall 132 and the auxiliary support column 133 are obtained by etching the same support layer, and thus have the same material and the same etching rate for the same etching process.

[0040] In an optional second embodiment, forming the support structure 130 on the bulk acoustic wave film 120 includes the following steps: first, forming a first support layer of a preset thickness on the bulk acoustic wave film 120; then, etching the first support layer to form the main support wall 131; then, filling a second support layer within the range defined by the main support wall 131 so that the second support layer is flush with the upper surface of the main support wall 131; then, etching the second support layer to form the isolation wall 132 and the auxiliary support column 133.

[0041] In the second embodiment described above, the main support wall 131, the isolation wall 132 and the auxiliary support column 133 are obtained by different etching processes, wherein the material of the main support wall 131 is the same as that of the first support layer, and the material of the isolation wall 132 and the auxiliary support column 133 is the same as that of the second support layer. The first support layer and the second support layer may contain different materials, so that the etching rates of the main support wall 131, the isolation wall 132 and the auxiliary support column 133 under the same etching process are different. By selecting the materials of the first support layer and the second support layer, the etching process for removing the auxiliary support column 133 may have a higher etching rate for the auxiliary support column 133 and the isolation wall 132 than for the main support wall 131. Thus, in the subsequent process of etching and removing the auxiliary support column 133, the isolation wall 132 may be removed in the same step. However, since the etching rate of the etching process for the main support wall 131 is relatively low, the main support wall 131 may be effectively protected when the isolation wall 132 is removed.

[0042] In an optional third embodiment, forming the support structure 130 on the bulk acoustic wave film 120 includes the following steps: first, forming a first support layer of a preset thickness on the bulk acoustic wave film 120; then, etching the first support layer to form the main support wall 131 and the isolation wall 132; then, filling a second support layer within the range defined by the isolation wall 132 so that the second support layer is flush with the upper surface of the main support wall 131; then, etching the second support layer to form the auxiliary support column 133.

[0043] In the above-mentioned third embodiment, the main support wall 131, the isolation wall 132 and the auxiliary support column 133 are obtained respectively by different etching processes, wherein the material of the main support wall 131 and the isolation wall 132 is the same as that of the first support layer, and the material of the auxiliary support column 133 is the same as that of the second support layer. The first support layer and the second support layer may contain different materials, so that the etching rates of the main support wall 131 and the isolation wall 132 and the auxiliary support column 133 under the same etching process are different. By selecting the materials of the first support layer and the second support layer, the etching rate of the auxiliary support column 133 in the etching process for removing the auxiliary support column 133 may be greater than the etching rate of the isolation wall 132 (or the main support wall 131). Therefore, when the auxiliary support column 133 is subsequently etched away, although the etching medium, such as etching liquid, will also contact and etch the isolation wall 132, the etching rate of the isolation wall 132 is lower than that of the auxiliary support column 133, that is, it is more difficult to etch, which helps to avoid the isolation wall 132 being etched through during the removal of the auxiliary support column 133, causing the etching liquid to damage the main support wall 131, that is, it can achieve a better isolation effect. In addition, compared with the case where the isolation wall 132 and the auxiliary support column 133 are made of the same material (i.e., the first embodiment), the width of the isolation wall 132 can be relatively reduced under the same isolation effect.

[0044] In an optional fourth embodiment, forming the support structure 130 on the bulk acoustic wave film 120 includes the following steps: first, forming a first support layer of a preset thickness on the bulk acoustic wave film 120; then, etching the first support layer to form the main support wall 131; then, filling a second support layer within the range defined by the main support wall 131, wherein the second support layer is flush with the upper surface of the main support wall 131; then, etching the second support layer to form the isolation wall 132; then, filling a third support layer within the range defined by the isolation wall 132, wherein the third support layer is flush with the upper surface of the isolation wall 132; then, etching the third support layer to form the auxiliary support column 133.

[0045] In the above-mentioned fourth embodiment, the main support wall 131, the isolation wall 132 and the auxiliary support column 133 are obtained by different etching processes respectively, wherein the materials of the main support wall 131, the isolation wall 132 and the auxiliary support column 133 are respectively the same as the materials of the first support layer, the second support layer and the third support layer, and the first support layer, the second support layer and the third support layer can contain different materials, so that the etching rates of the main support wall 131, the isolation wall 132 and the auxiliary support column 133 under the same etching process are different. For example, by selecting the materials of the first support layer, the second support layer and the third support layer, the etching process for removing the auxiliary support column 133 can reduce the etching rates of the auxiliary support column 133, the isolation wall 132 and the main support wall 131 in sequence. Therefore, when the auxiliary support column 133 is subsequently etched away, although the etching medium, such as etching liquid, will also contact and etch the isolation wall 132, since the etching rate of the isolation wall 132 is lower than that of the auxiliary support column 133, that is, it is more difficult to etch, it helps to avoid the isolation wall 132 being etched through during the process of removing the auxiliary support column 133 and causing the etching liquid to damage the main support wall 131, that is, it can achieve a better isolation effect. Moreover, after removing the auxiliary support column 133, in the process of removing the isolation wall 132, since the main support wall 131 is more difficult to etch, it is less likely for the main support wall 131 to be corroded and damaged.

[0046] Figure 5 FIG. 1 is a cross-sectional schematic diagram of a first substrate and a second substrate bonded together using the method for manufacturing a thin film bulk acoustic wave resonator according to an embodiment of the present invention. Figure 1 and Figure 5 , perform step S4, bond the side of the first substrate 100 formed with the support structure 130 to the second substrate 200, and remove the first substrate 100.

[0047] In this embodiment, the second substrate 200 is used as a carrier wafer. The first substrate 100 and the second substrate 200 are bonded to fix the bulk acoustic wave film 120 on the first substrate 100 between the two substrates. Subsequently, the first substrate 100 is thinned by a back-side etching process until it is basically removed, and the auxiliary support columns 133 and the isolation walls 132 in the support structure 130 are removed. Air interfaces can be formed on both sides of the bulk acoustic wave film to obtain the main structure of the thin film bulk acoustic wave resonator.

[0048] The second substrate 200 can be selected from the supporting substrates commonly used in the art. Specifically, the material of the second substrate 200 can be any suitable base material known to those skilled in the art, for example, it can be at least one of the following materials: silicon (Si), germanium (Ge), silicon germanium (SiGe), carbon silicon (SiC), carbon germanium silicon (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP) or other III / V compound semiconductors, including multilayer structures composed of these semiconductors, or silicon on insulator (SOI), stacked silicon on insulator (SSOI), stacked silicon germanium on insulator (S-SiGeOI), silicon germanium on insulator (SiGeOI) and germanium on insulator (GeOI), or it can also be double-side polished silicon wafers (Double Side Polished Wafers, DSP), or ceramic substrates such as aluminum oxide, quartz or glass substrates, etc. In this embodiment, the second substrate 2000 is, for example, a P-type high-resistance single-crystal silicon wafer with a (100) crystal plane on the upper surface. Of course, the second substrate 200 may also include other materials known in the art.

[0049] The first substrate 100 and the second substrate 200 may be bonded by a melt bonding process or a vacuum bonding process, so that the surface of the second substrate 200 forms a covalent bond with the surface of the support structure 130 on the first substrate 100 and is fixed, and has a high bonding strength. In another embodiment of the present invention, the first substrate 100 and the second substrate 200 may also be fixed by bonding. For example, hot melt adhesive may be first applied to the second substrate 200, and then the second substrate 200 may be bonded to the top surface of the support structure 130 (i.e., the surface of the side of the support structure 130 away from the bulk acoustic wave film 120) by a vacuum bonding process in a vacuum environment. When the second substrate 200 is bonded to the support structure 130 by a vacuum bonding process, the vacuum bonding conditions that may be set include: a bonding pressure of 1 Pa to 10 5 Pa, the bonding temperature is 150℃~200℃. The vacuum bonding process can avoid the generation of bubbles and the bonding effect is better.

[0050] After the first substrate 100 and the second substrate 200 are bonded, the second substrate 200 is used as a supporting substrate and turned upside down, and the supporting structure 130 and the bulk acoustic wave film 120 are transferred to the second substrate 200, and then the first substrate 100 can be removed.

[0051] The first substrate 100 can be thinned and removed from the isolation layer 110 by a backside etching process. The isolation layer 110 serves as a stop layer during the etching process to avoid affecting the bulk acoustic wave film 120. After the first substrate 100 is removed, the isolation layer 110 is etched to greatly reduce its thickness or even completely eliminate it. Figure 5In another embodiment, the first substrate 100 can be removed by chemical mechanical polishing process, and the isolation layer 110 can be removed at the same time. Optionally, when considering using the isolation layer 110 to protect the bulk acoustic wave film 110, the isolation layer 110 can also be partially retained. In this case, the thickness of the remaining isolation layer 110 can be the minimum thickness reached by the process capability of the chemical mechanical polishing equipment, for example, In another embodiment, a suitable process can be selected to remove the first substrate according to the material properties of the isolation layer 110 and the first substrate 100. For example, when the isolation layer 110 is a photocurable adhesive, the photocurable adhesive is removed by a chemical reagent, so that the first substrate 100 and the bulk acoustic wave film 110 are separated to remove the first substrate 100; when the isolation layer 110 is a hot melt adhesive, the hot melt adhesive is made to lose its viscosity by a heat release process such as a heating treatment, so that the first substrate and the bulk acoustic wave film 110 are separated to remove the first substrate 100. Furthermore, when the isolation layer 110 is a stacked structure of an etch stop layer and a sacrificial material layer and the sacrificial material is a laser demolding material, the sacrificial material layer can be removed by a laser ablation process, so that the first substrate 100 is peeled off. During the laser ablation process, the etch stop layer in the isolation layer 110 is used to protect the bulk acoustic wave film 110.

[0052] like Figure 5 As shown, after step S4, both upper and lower sides (i.e., both sides in the thickness direction) of the bulk acoustic wave film 120 above the second substrate 200 have air interfaces. Since the support structure 130 supports the bulk acoustic wave film 120 from multiple regions, the bulk acoustic wave film 120 has good stability, and various treatments performed on the bulk acoustic wave film 120 (such as the patterning process performed on the bulk acoustic wave film 120) are not likely to cause the bulk acoustic wave film 120 to collapse, which can reduce the difficulty of process control. After completing such a process that has high requirements on the stability of the bulk acoustic wave film 120, the auxiliary support column 133 and the isolation wall 132 in the support structure 130 can be removed.

[0053] Reference Figure 6 and Figure 7 After removing the first substrate 100 , step S5 is performed to form a release window 120 a in the BAW film 120 , wherein the release window 120 a allows the space defined by the isolation wall 132 to communicate with the outside.

[0054] Optionally, after removing the first substrate 100 in step S4, the first electrode layer 121 and the piezoelectric layer 122 of the bulk acoustic wave film 110 may be partially removed by a cutting process or a photomask process to form an edge trimming area 123a exposing a portion of the second electrode layer 123. The sidewall of the edge trimming area 123a may be a sidewall perpendicular to the upper surface of the second electrode layer 123, or may be an inclined sidewall whose top is closer to the center of the range defined by the isolation wall 132 than the bottom of the sidewall. The edge trimming area 123a and the range defined by the isolation wall 132 may partially overlap in the thickness direction of the isolation wall 132. Since the film thickness of the overlapping area of ​​the edge trimming area 123a and the range defined by the isolation wall 132 is relatively thin, it is helpful to reduce the subsequent process difficulty of forming a release window in the bulk acoustic wave film 110, and to make a release window of a larger size, thereby helping to reduce the subsequent process difficulty of removing the auxiliary support column 133 and the isolation wall 132 and improve the removal efficiency.

[0055] In addition, optionally, after removing the first substrate 100 in step S4, the bulk acoustic wave film 110 can also be patterned (for example, by patterning through multiple photolithography combined with etching processes) to form an upper electrode and a lower electrode and define the resonant working area and non-resonant area of ​​the bulk acoustic wave film located above the range limited by the main support wall 131. The bulk acoustic wave film 110 in the resonant working area can be used as a resonant structure of a thin film bulk acoustic wave resonator. In addition, after forming the upper electrode and the lower electrode, a metal bonding layer can be formed outside the effective working area by, for example, a metal lift-off technology, and the metal bonding layer is subsequently used to bond to a third substrate as a sealing substrate on the side of the bulk acoustic wave film 110 away from the second substrate 200. In the above-mentioned upper and lower electrode definition processes and metal bonding layer formation processes, due to the support of the support structure 130, these processes will not cause the film layer within the range of the support structure 130 to have a problem of downward pressure deformation and cracking that exceeds the specification requirements. In another embodiment of the present invention, when forming the BAW film 120 on the first substrate 100 in step S2, before covering the piezoelectric layer 122, the first electrode layer 121 is patterned (for example, patterned by photolithography and etching processes) to form an upper electrode of the BAW resonator, and before covering the second electrode layer 123, the piezoelectric layer 122 is patterned (for example, patterned by photolithography and etching processes) to form a piezoelectric layer located in an effective working area of ​​the BAW resonator, and after covering the second electrode layer 123 and before Before covering the supporting material, the second electrode layer 123 is patterned (for example, patterned by photolithography and etching processes) to form the lower electrode of the BAW resonator and define the resonant working area and non-resonant area of ​​the BAW film. It should be understood that in specific implementation, only the first electrode layer 121, the piezoelectric layer 122 and the second electrode layer 123 of the BAW film 120 can be patterned in step S2, or any two or all of them can be patterned, and the remaining unpatterned film layers can be patterned after the first substrate is removed in step S4.

[0056] In this embodiment, after removing the first substrate 100 and before forming the release window 120a, the following process may be included: firstly, performing a first sub-step, using a first mask pattern, etching the first electrode layer 121 and the piezoelectric layer 122, so that the second electrode layer 123 is exposed from the side away from the second substrate (such as Figure 6 ), the exposed second electrode layer includes a portion located within the range defined by the isolation wall 132; then a second sub-step is performed, using a second mask pattern, etching the exposed second electrode layer 123 to form the release window 120a (as shown in FIG. 1 ) within the range defined by the isolation wall 132. Figure 7 shown).

[0057] In another embodiment of the present invention, the process of exposing the second electrode layer 123 from the side away from the second substrate can be implemented in the process of forming the edge trimming area 123a or forming the upper electrode and the lower electrode. Forming the release window 120a in the exposed portion of the second electrode layer 123 can reduce the process difficulty on the one hand, and avoid affecting the resonance working area on the other hand.

[0058] Specifically, the release window 120a may be formed by penetrating the bulk acoustic wave film 120 corresponding to the gap between the isolation wall 132 and the auxiliary support column, and the release window 120a may also penetrate the bulk acoustic wave film 120 and expose the top of a portion of the auxiliary support column 133. The etching process of the release window 120a may be dry etching or wet etching, and the dry etching process includes but is not limited to reactive ion etching (RIE), ion beam etching, plasma etching, etc. For example, a fluorine-based etching gas is used and a reactive ion etching process is used to etch the exposed portion of the second electrode layer 123 to form the release window 120a, and the fluorine-based etching gas may include at least one of CF4, CHF3, C2F6, CH2F2, C4F8, NF3 and SF4, and the etching power is, for example, 0 to 500W to ensure the yield. In addition, the release window 120 a may be formed by etching the exposed second electrode layer 123 located in the edge trimming area 123 a by laser drilling, so as to form the release window 120 a within the range defined by the isolation wall 132 .

[0059] In another embodiment of the present invention, the release window 120a may be formed directly in the bulk acoustic wave film 120 without forming the edge trimming area 123a, that is, the first electrode layer 121, the piezoelectric layer 122 and the second electrode layer 123 need to be penetrated to form the release window 120a. In this case, a multi-step etching process may be used to form the release window 120a, so as to etch the first electrode layer 121, the piezoelectric layer 122 and the second electrode layer 123 in steps and form the release window 120a. In order to facilitate the smooth discharge of impurities within the limited range of the support structure through the release window 120a in the subsequent etching process, the size of the release window 120a may be made larger, for example, it may be formed as a circular hole with a diameter of 10 μm to 30 μm, or a square hole with a side length of about 10 μm to 30 μm, etc.

[0060] In order to reduce the impact on the main support wall 131 during the removal of the auxiliary support pillars 133, the positive projection of the release window 120a on the surface of the second substrate 200 should fall within the range defined by the isolation wall 132, that is, the release window 120a allows the isolation wall 132 and the auxiliary support pillars 133 to react with the etching process gas or etching liquid entering from the release window 120a, so as to carry out the process of removing the auxiliary support pillars 133 within the range defined by the isolation wall 132.

[0061] The opening size of the release window 120a can be set according to the area range where the release window is allowed to be set. There can also be more than one release window 120a. Optionally, more than two release windows 120a are formed in the BAW film 120 to speed up the removal of the auxiliary support column 133 and the isolation wall 132. Multiple release windows 120a can be dispersed on the exposed second electrode layer 304 within the range defined by the isolation wall 132. Optionally, the release window 120a can be set at a corner position within the range defined by the isolation wall 132. On the one hand, it can avoid the influence on the resonant working area and improve the Q value of the BAW resonator. On the other hand, it is conducive to the smooth discharge of substances from the cavity in the subsequent etching process and cleaning process and is conducive to the drying of the cavity. In addition, it can also reduce the area of ​​parasitic devices as much as possible.

[0062] Reference Figure 8 , execute step S6, using the release window 120a to remove the auxiliary support column 133 and the isolation wall 132.

[0063] According to the material of the auxiliary support column 133 and the isolation wall 132, a wet process or a dry process can be specifically used to remove them. Taking wet etching as an example, for the auxiliary support column and the isolation wall 132 made of silicon oxide, an etching solution including dilute hydrochloric acid, BOE (buffered oxide etchant) or DHF (diluted hydrofluoric acid) capable of etching silicon oxide can be introduced into the range defined by the isolation wall between the second substrate 200 and the second electrode layer 123 through the release window 120a to remove the auxiliary support column 133 and the isolation wall 132. BOE is a solution of hydrofluoric acid HF, ammonium fluoride NH4F and water, wherein the ratio of 40% NH4F: 49% HF: H2O is 10:1:0-200:1:10, and in DHF, the ratio of 49% HF to H2O is, for example, 30:1-500:1). The etching liquid enters the space defined by the isolation wall 132 and the bulk acoustic wave film 120 through the release window 120a and contacts the side walls of the isolation wall 132 and the side walls of the auxiliary support pillars 133, or first contacts the top of the auxiliary support pillars 133 exposed by the release window 120a, and then enters the gap around the auxiliary support pillars 133 and contacts the side walls of other auxiliary support pillars 133 and the side walls of the isolation wall 132. In addition, the process of selecting BOE solution or DHF solution to remove the auxiliary support pillars 133 and the isolation wall 132 can have a shorter over-etching time (i.e., cleaning time), so that the cavity formed by the BOE solution or DHF solution within the range of the main support wall 131 can be used for preliminary cleaning to remove pollutants such as etching byproduct particles and metal ions, so that a good cavity cleaning effect can be obtained in a shorter cleaning time, thereby further improving the performance of the device finally formed.

[0064] In the process of removing the auxiliary support pillars 133 and the isolation walls 132, consideration should be given to avoiding damage to the piezoelectric layer 122, the second electrode layer 123 and the first electrode layer 121. Therefore, it is appropriate to select an etching solution with a high etching selectivity ratio between the material of the auxiliary support pillars 133 and the isolation walls 132 and the bulk acoustic wave film to remove each auxiliary support pillar 133 and the isolation wall 132, that is, the selected etching solution can remove the auxiliary support pillars 133 and the isolation walls 132 without damaging or less damaging the bulk acoustic wave film.

[0065] In another embodiment of the present invention, if the auxiliary support pillars 133 are made of materials that are easy to remove by ashing, such as photoresist, dry film or amorphous carbon, the auxiliary support pillars 133 can also be removed by introducing plasma process gas into the range defined by the isolation wall 132 between the second substrate 200 and the second electrode layer 123 through the release window 120a after covering other areas with a protective layer. The specific process parameters can be specifically set according to the etching method and requirements.

[0066] In the present embodiment, during the process of etching the auxiliary support pillars 133, the etching liquid or etching gas will also etch the exposed isolation walls 132. However, due to the obstruction of the isolation walls 132, the possibility of the main support wall 131 being corroded can be reduced. Furthermore, by setting the width and number of the isolation walls 132 and the etching time, the auxiliary support pillars 133 and the isolation walls 132 can be removed at the same time in step S6, or after removing the auxiliary support pillars 133, the isolation walls 132 can be removed by extending the time of the same etching reaction, that is, the auxiliary support pillars 133 and the isolation walls 132 are removed in turn. After the reaction of removing the isolation walls 132 is completed, the etching reaction is stopped as soon as possible to avoid the influence of long-term erosion on the main support walls 131.

[0067] After removing the auxiliary support pillars 133 and the isolation wall 132, the second substrate 200, the main support wall 131 and the BAW film 120 enclose a cavity 140. By using the above-mentioned method for manufacturing a thin film BAW resonator, the range and shape of the cavity 140 will not be significantly changed due to the above-mentioned etching process, so the reliability is good. The cavity 140 can be used as a resonant cavity of the BAW resonator, and improving its stability is conducive to improving the performance of the BAW resonator.

[0068] Optionally, after removing the auxiliary support column 133 and the isolation wall 132, deionized water can be introduced into the cavity 140 through the release window 120a to clean (i.e., rinse) the cavity 140, and then isopropyl alcohol (IPA) gas can be introduced into the cavity 140 through the release window 120a to dry the cavity 140, so that the residual liquid in the cavity 140 is cleaned, thereby ensuring the resonance performance. In addition, due to the existence of the release window 120a, during the stage of cleaning and drying the cavity 140, each release window 120a can be used as a vent to connect the internal and external environments of the cavity 140, thereby balancing the air pressure inside and outside the cavity 140, and avoiding problems such as the cavity 140 being ruptured due to excessive pressure difference inside and outside the cavity 140.

[0069] The above parts are used to form a resonator main structure having a cavity 140, a bulk acoustic wave film and a second substrate 200. Subsequently, a third substrate (as a sealing substrate, cap wafer) can be bonded above the main support wall 131, and a gap is provided between the bulk acoustic wave film 120 and the third substrate, which serves as another cavity of the bulk acoustic wave resonator connected to the cavity 140. The third substrate encapsulates and protects the main structure of the resonant cavity, so the auxiliary support columns 133 and the isolation walls 132 of the above support structure can be removed before bonding the third substrate, so as to play a supporting role in each resonator manufacturing process. In this embodiment, the above release window can be located within the closed range of the third substrate.

[0070] In addition, pads electrically connected to the first electrode layer 121 and the second electrode layer 123 can be formed on both sides of the resonance working area through the third substrate, thereby obtaining a thin film bulk acoustic wave resonator. Among them, the first electrode layer 121 can be used as an input electrode or an output electrode for receiving or providing an electrical signal such as a radio frequency (RF) signal. For example, when the patterned second electrode layer 123 is used as an input electrode, the patterned first electrode layer 121 can be used as an output electrode, and when the patterned second electrode layer 123 is used as an output electrode, the patterned first electrode layer 121 can be used as an input electrode, and the piezoelectric layer 104 converts the electrical signal input through the patterned first electrode layer 121 or the patterned second electrode layer 123 into a bulk acoustic wave. For example, the piezoelectric layer 122 converts the electrical signal into a bulk acoustic wave through physical vibration. Since the reliability of the support structure and the cavity obtained by the above-mentioned manufacturing process is improved, it helps to improve the performance of the bulk acoustic wave resonator.

[0071] This embodiment also includes a thin film bulk acoustic wave resonator formed by the above method. The thin film bulk acoustic wave resonator includes a second substrate 200 and a bulk acoustic wave film disposed on the second substrate 200, a support structure is disposed between the bulk acoustic wave film and the second substrate 200, the support structure includes a main support wall 131, the second substrate 200, the main support wall 131 and the bulk acoustic wave film form a cavity 140, and the bulk acoustic wave film is suspended above the cavity 140 by contacting the support structure. Since the above-mentioned method for manufacturing the thin film bulk acoustic wave resonator helps to improve the reliability of the cavity 140, the reliability of the manufactured thin film bulk acoustic wave resonator can also be improved, thereby helping to improve the resonance performance.

[0072] This embodiment also includes a filter, the filter includes at least one thin film bulk acoustic wave resonator, and the formation of the thin film bulk acoustic wave resonator includes the above-mentioned method for making the thin film bulk acoustic wave resonator. The filter can be a radio frequency filter. By improving the method for making the thin film bulk acoustic wave resonator, the performance and reliability of the resonator are improved, which is conducive to improving the performance and yield of the filter.

[0073] The methods and structures in this embodiment are described in a progressive manner, and the latter methods and structures are mainly described to explain the differences from the former methods and structures, and the relevant parts can be understood by reference.

[0074] The above description is only a description of the preferred embodiment of the present invention, and is not any limitation on the scope of rights of the present invention. Any technical personnel in this field can make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for manufacturing a thin film bulk acoustic wave resonator, characterized in that: include: providing a first substrate; forming an isolation layer and a bulk acoustic wave thin film on the isolation layer on the first substrate; A support structure is formed on the bulk acoustic wave film, wherein the support structure comprises a main support wall, a separation wall and an auxiliary support column which are sequentially arranged on the upper surface of the bulk acoustic wave film from the outside to the inside, wherein both the main support wall and the separation wall are annular structures, the separation wall is arranged inside the main support wall, and the auxiliary support column is arranged inside the separation wall; Bonding the side of the first substrate on which the support structure is formed to a second substrate, and removing the first substrate; forming a release window in the bulk acoustic wave film, wherein the release window enables the space defined by the isolation wall to communicate with the outside world; as well as The auxiliary support column and the isolation wall are removed by using the release window, wherein the main support wall and the auxiliary support column are made of different materials, and the etching rate of the auxiliary support column in the etching process for removing the auxiliary support column is greater than the etching rate of the main support wall.

2. The method for manufacturing a thin film bulk acoustic wave resonator according to claim 1, characterized in that: The step of forming the support structure on the bulk acoustic wave film comprises: forming a support layer of a preset thickness on the bulk acoustic wave film; and The support layer is etched to form the support structure.

3. The method for manufacturing a thin film bulk acoustic wave resonator according to claim 2, characterized in that: The width of the isolation wall is greater than or equal to the dimension of the auxiliary support column along the width direction of the isolation wall.

4. The method for manufacturing a thin film bulk acoustic wave resonator according to claim 1, characterized in that: The step of forming the support structure on the bulk acoustic wave film comprises: forming a first supporting layer of a preset thickness on the bulk acoustic wave film; Etching the first supporting layer to form the main supporting wall; Filling a second supporting layer within the range defined by the main supporting wall, wherein the second supporting layer is flush with the upper surface of the main supporting wall; and The second supporting layer is etched to form the isolation wall and the auxiliary supporting column.

5. The method for manufacturing a thin film bulk acoustic wave resonator according to claim 4, characterized in that: The main support wall and the isolation wall are made of different materials, and the etching rate of the auxiliary support column and the isolation wall in the etching process for removing the auxiliary support column is greater than the etching rate of the main support wall.

6. The method for manufacturing a thin film bulk acoustic wave resonator according to claim 1, characterized in that: The step of forming the support structure on the bulk acoustic wave film comprises: forming a first supporting layer of a preset thickness on the bulk acoustic wave film; Etching the first supporting layer to form the main supporting wall and the isolation wall; Filling a second supporting layer within the range defined by the isolation wall, wherein the second supporting layer is flush with the upper surface of the main supporting wall; and The second supporting layer is etched to form the auxiliary supporting pillars.

7. The method for manufacturing a thin film bulk acoustic wave resonator according to claim 6, characterized in that: The isolation wall and the auxiliary support column are made of different materials, and the etching rate of the auxiliary support column in the etching process for removing the auxiliary support column is greater than the etching rate of the isolation wall.

8. The method for manufacturing a thin film bulk acoustic wave resonator according to claim 1, characterized in that: The step of forming the support structure on the bulk acoustic wave film comprises: forming a first supporting layer of a preset thickness on the bulk acoustic wave film; Etching the first supporting layer to form the main supporting wall; Filling a second supporting layer within the range defined by the main supporting wall, wherein the second supporting layer is flush with the upper surface of the main supporting wall; Etching the second supporting layer to form the isolation wall; Filling a third supporting layer within the range defined by the isolation wall, wherein the third supporting layer is flush with the upper surface of the isolation wall; and The third supporting layer is etched to form the auxiliary supporting pillars.

9. The method for manufacturing a thin film bulk acoustic wave resonator according to claim 8, characterized in that: The materials of the main support wall, the isolation wall and the auxiliary support column are all different, and the etching rate of the auxiliary support column, the isolation wall and the main support wall is reduced in sequence during the etching process for removing the auxiliary support column.

10. The method for manufacturing a thin film bulk acoustic wave resonator according to claim 1, characterized in that: The bulk acoustic wave film includes a first electrode layer, a piezoelectric layer and a second electrode layer which are sequentially stacked on the isolation layer.

11. The method for manufacturing a thin film bulk acoustic wave resonator according to claim 10, characterized in that: After removing the first substrate and before forming the release window, the method for manufacturing the BAW resonator includes: removing part of the first electrode layer and part of the piezoelectric layer, so that the second electrode layer is exposed from the side away from the second substrate, and the exposed second electrode layer includes a part located in a range defined by the isolation wall; and The second electrode layer is exposed by etching, and the release window is formed in the bulk acoustic wave film corresponding to the range defined by the isolation wall.

12. The method for manufacturing a thin film bulk acoustic wave resonator according to claim 1, characterized in that: More than two release windows are formed in the BAW film.

13. The method for manufacturing a thin film bulk acoustic wave resonator according to claim 1, characterized in that: Within the range defined by the isolation wall, the release window is closer to the isolation wall than the central area.

14. The method for manufacturing a thin film bulk acoustic wave resonator according to claim 1, characterized in that: In the supporting structure, two or three circles of the isolation wall are nested between the main supporting wall and the auxiliary supporting columns.

15. The method for manufacturing a thin film bulk acoustic wave resonator according to claim 1, characterized in that: In the step of removing the auxiliary support pillars and the isolation wall by using the release window, the auxiliary support pillars and the isolation wall are removed by using a wet etching process.

16. The method for manufacturing a thin film bulk acoustic wave resonator according to claim 1, characterized in that: A gap of uniform width is provided between the isolation wall and the main supporting wall.

17. The method for manufacturing a thin film bulk acoustic wave resonator according to claim 1, characterized in that: In a plane parallel to the surface of the first substrate, the plane shape of the isolation wall is a pentagon, a hexagon or a heptagon.

18. The method for manufacturing a thin film bulk acoustic wave resonator according to claim 1, characterized in that: The heights of the main support wall, the isolation wall and the auxiliary support column are all in the range of 2µm to 5µm.

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