Bulk acoustic wave device preparation method and bulk acoustic wave device

Abstract

The invention provides a bulk acoustic wave device preparation method and a bulk acoustic wave device, which can be applied to the technical field of semiconductors. The method comprises the following steps: forming a bulk acoustic wave filter on a silicon-based substrate; depositing protective layers on the surface and the back surface of the bulk acoustic wave filter; a plurality of through hole openings are formed in the protection layer through etching based on a plurality of electrode connection areas on the surface of the bulk acoustic wave filter; and packaging the bulk acoustic wave filter based on the plurality of openings to obtain the bulk acoustic wave device.

Description

Technical Field

[0001] The present disclosure relates to the field of semiconductor technology, and more particularly, to a method for manufacturing a bulk acoustic wave device and a bulk acoustic wave device. Background Art

[0002] In the process of manufacturing a bulk acoustic wave filter (BAW), due to factors such as the uniformity of thin film or etching processes, the thickness of a single wafer obtained during manufacturing cannot be made exactly the same in different regions, and even the operating frequencies in different regions of a single bulk acoustic wave filter are different. To solve this problem, in related technologies, materials with low acoustic loss, such as AlN (aluminum nitride), are usually used to form a passivation layer on the top of the bulk acoustic wave filter during the manufacturing process, and then the surface of the passivation layer is etched by means such as ion beam etching to correct the operating frequency of the bulk acoustic wave filter.

[0003] However, in practical applications, the AlN (aluminum nitride) material will undergo a slow hydrolysis reaction in a water vapor environment, resulting in the operating frequency of the bulk acoustic wave device changing over time and affecting the reliability of the device. In related technologies, a wafer-level packaging method with extremely high sealing performance is usually used to form a sealing structure on the bulk acoustic wave filter. However, this wafer-level packaging method has a complex process and the equipment required is expensive, indirectly reducing the yield rate of manufacturing the acoustic wave filtering module and increasing the production cost of manufacturing the acoustic wave filtering module. Summary of the Invention

[0004] In view of this, the present disclosure provides a method for manufacturing a bulk acoustic wave device and a bulk acoustic wave device.

[0005] One aspect of the present disclosure provides a method for manufacturing a bulk acoustic wave device, including:

[0006] Forming a bulk acoustic wave filter on a silicon-based substrate;

[0007] Depositing and forming a protective layer on the surface and the back surface of the above-mentioned bulk acoustic wave filter;

[0008] Based on a plurality of electrode connection regions included in the surface of the above-mentioned bulk acoustic wave filter, etching a plurality of openings in the above-mentioned protective layer; and

[0009] Performing a packaging process on the above-mentioned bulk acoustic wave filter based on the above-mentioned plurality of openings to obtain a bulk acoustic wave device.

[0010] According to an embodiment of the present disclosure, the etching a plurality of openings in the above-mentioned protective layer based on a plurality of electrode connection regions included in the surface of the above-mentioned bulk acoustic wave filter includes:

[0011] Based on the positions of the respective multiple electrode connection regions, apply photoresist on the surface of the above-mentioned protective layer and perform exposure and development; and

[0012] Etch the protective layer coated with photoresist to form multiple openings on the above-mentioned protective layer.

[0013] According to an embodiment of the present disclosure, etching multiple openings on the above-mentioned protective layer based on the multiple electrode connection regions included in the surface of the above-mentioned bulk acoustic wave filter includes:

[0014] Set a steel mesh between 1 um and 50 um above the above-mentioned protective layer, wherein the above-mentioned steel mesh includes multiple hollowed-out regions, and the multiple hollowed-out regions correspond to the respective multiple electrode connection regions;

[0015] Dry-etch the above-mentioned protective layer through the above-mentioned steel mesh to form the above-mentioned multiple openings on the above-mentioned protective layer; and

[0016] Remove the above-mentioned steel mesh.

[0017] According to an embodiment of the present disclosure, encapsulating the above-mentioned bulk acoustic wave filter based on the above-mentioned multiple openings to obtain a bulk acoustic wave device includes:

[0018] Respectively form bump structures in the respective multiple electrode connection regions through the above-mentioned multiple openings; and

[0019] Based on the multiple above-mentioned bump structures, encapsulate the above-mentioned bulk acoustic wave filter on a substrate to obtain the above-mentioned bulk acoustic wave device.

[0020] According to an embodiment of the present disclosure, the above method further includes:

[0021] Before respectively forming bump structures in the respective multiple electrode connection regions through the above-mentioned multiple openings, perform a frequency response test on the above-mentioned bulk acoustic wave filter to obtain the device resonance or anti-resonance frequency; and

[0022] Based on the deviation between the above-mentioned device frequency and the expected device frequency, etch the above-mentioned protective layer, or deposit a new protective layer on the surface of the above-mentioned bulk acoustic wave filter.

[0023] According to an embodiment of the present disclosure, encapsulating the above-mentioned bulk acoustic wave filter on a substrate based on the multiple above-mentioned bump structures to obtain a bulk acoustic wave device includes:

[0024] Based on the position of the above-mentioned bulk acoustic wave filter, cut the above-mentioned silicon-based substrate to obtain grains related to the above-mentioned bulk acoustic wave filter;

[0025] Based on multiple convex point structures as described above, the above-mentioned die is mounted and soldered on the above-mentioned substrate through surface mount technology or flip-chip technology to obtain an initial bulk acoustic wave device; and

[0026] The above-mentioned initial bulk acoustic wave device is subjected to a film coating process to obtain the above-mentioned bulk acoustic wave device.

[0027] According to an embodiment of the present disclosure, forming a bulk acoustic wave filter on the silicon-based substrate includes:

[0028] Etch a cavity structure on the above-mentioned silicon-based substrate;

[0029] Fill the above-mentioned cavity structure with a sacrificial layer material to obtain a sacrificial layer;

[0030] Form a seed layer, a lower electrode layer, a piezoelectric layer, an upper electrode layer, a passivation layer, and an electrode connection layer successively upward from the surface of the above-mentioned sacrificial layer. Among them, the surface of the above-mentioned electrode connection layer includes the above-mentioned multiple electrode connection regions; and

[0031] Release the above-mentioned sacrificial layer material through a release structure to obtain the above-mentioned bulk acoustic wave filter.

[0032] According to an embodiment of the present disclosure, depositing and forming a protective layer on the surface and back of the above-mentioned bulk acoustic wave filter includes:

[0033] Deposit and form the above-mentioned protective layer on the surface and back of the above-mentioned bulk acoustic wave filter and the inner surface of the above-mentioned cavity structure.

[0034] According to an embodiment of the present disclosure, depositing and forming a protective layer on the surface of the above-mentioned bulk acoustic wave filter includes:

[0035] Use atomic layer deposition method to form the above-mentioned protective layer on the surface of the above-mentioned bulk acoustic wave filter, wherein the thickness of the above-mentioned protective layer is between 1 nm and 100 nm

[0036] Another aspect of the present disclosure provides a bulk acoustic wave device prepared by using the method for preparing any one of the above-mentioned bulk acoustic wave devices.

[0037] According to an embodiment of the present disclosure, a protective layer is formed on the surface of a bulk acoustic wave filter, and this protective layer is used to prevent the bulk acoustic wave filter from being eroded by water vapor in the operating environment. Then, openings are formed by etching the protective layer, and the electrodes exposed by the openings are processed to form bump structures. The filter device is connected to the substrate using Surface Mount Technology (SMT) or Flip Chip Technology (FCT), and the encapsulation of the bulk acoustic wave filter is completed through a film coating technology to obtain a bulk acoustic wave device. The manufacturing method of this bulk acoustic wave device does not require wafer-level packaging and does not need to use expensive metals as sealing metal rings. It can use a simpler process flow to generate the protective layer and the encapsulation structure, reducing the process complexity and the cost of the materials used, thereby improving the yield rate of manufacturing bulk acoustic wave devices and effectively reducing the production cost of manufacturing bulk acoustic wave devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Through the following description of the embodiments of the present disclosure with reference to the drawings, the above and other objects, features, and advantages of the present disclosure will become clearer. In the drawings:

[0039] Figure 1 Schematically shows a flowchart of a method for manufacturing a bulk acoustic wave device according to an embodiment of the present disclosure;

[0040] Figure 2 Schematically shows a schematic diagram of a bulk acoustic wave filter according to an embodiment of the present disclosure;

[0041] Figure 3 Schematically shows a schematic diagram of an SMR type bulk acoustic wave filter according to an embodiment of the present disclosure;

[0042] Figure 4 Schematically shows a schematic diagram of a bulk acoustic wave filter with a protective layer according to an embodiment of the present disclosure;

[0043] Figure 5 Schematically shows a schematic diagram of forming openings by stencil etching according to an embodiment of the present disclosure;

[0044] Figure 6 Schematically shows a schematic diagram of the bulk acoustic wave filter after etching according to an embodiment of the present disclosure;

[0045] Figure 7 Schematically shows a schematic diagram of ball planting on a bulk acoustic wave filter according to an embodiment of the present disclosure;

[0046] Figure 8 Schematically shows a schematic diagram of an initial bulk acoustic wave device according to an embodiment of the present disclosure; and

[0047] Figure 9A schematic diagram schematically shows a bulk acoustic wave device according to an embodiment of the present disclosure. Detailed implementation manners

[0048] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the following detailed description, for the sake of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, obviously, one or more embodiments can also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present disclosure.

[0049] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "including", "comprising", etc. used herein indicate the presence of the described features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0050] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those of ordinary skill in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0051] In the case of using expressions such as "at least one of A, B, and C, etc.", generally, it should be interpreted according to the meaning commonly understood by those of ordinary skill in the art (for example, "a system having at least one of A, B, and C" should include, but not be limited to, a system having only A, having only B, having only C, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0052] The bulk acoustic wave filter includes two types: the solidly mounted bulk acoustic wave filter (SMR Bulk Acoustic Wave Filter) and the film bulk acoustic resonator (FBAR). During the preparation of bulk acoustic wave devices, AlN material is generally used as the passivation layer, which also has the function of frequency modulation. In related technologies, a wafer-level package (WLP) method with extremely high sealing performance is often used to form a sealing structure on the bulk acoustic wave filter to improve the reliability of the device. For example, a metal sealing ring is formed around the device, and a silicon wafer or a glass wafer is bonded as the cover of the bulk acoustic wave filter by using gold-gold bonding / gold-tin bonding / copper-tin bonding, etc. Then, the device I / O ports that need to be circuit-connected are led above the cover plate or to the bottom of the substrate through the through-silicon via (TSV) to be connected to other circuits. Then, the bonded wafer is ball-implanted and cut into chips, which are mounted on the substrate and covered with a film to form a complete filter chip.

[0053] In the process of implementing the concept of the present disclosure, the inventors found that at least the following problems exist in the related technologies:

[0054] 1) The bonding of the wafer-level metal sealing ring requires ensuring that the entire bulk acoustic wave filter is sealed by a large number of sealing rings. At the same time, to ensure good sealing performance during the bonding process, the process used is of high difficulty. Moreover, corresponding to the extremely high flatness and metal layer film formation uniformity requirements for bulk acoustic wave devices, expensive chemical mechanical polishing (CMP) equipment and metal film formation equipment also need to be matched. In related technologies, it is difficult to achieve a high bonding yield, and the failure probability of bulk acoustic wave devices is relatively high.

[0055] 2) A sealing metal ring with a certain width needs to be set around the bulk acoustic wave device, which will cause an increase in chip size, a decrease in the yield of bulk acoustic wave devices produced per single wafer, and an increase in production cost.

[0056] 3) The wafer-level package (WLP) structure requires an additional wafer to be used as the cover. To make the bonding more stable, precious metals are generally used as the bonding material, such as gold. Moreover, the electrical connection needs to be led out through TSV holes, resulting in a significant increase in manufacturing cost.

[0057] In view of this, embodiments of the present disclosure provide a method for manufacturing a bulk acoustic wave device and a bulk acoustic wave device. The method includes: forming a bulk acoustic wave filter on a silicon-based substrate; depositing a protective layer on the surface of the bulk acoustic wave filter; etching a plurality of openings in the protective layer based on a plurality of electrode connection regions included in the surface of the bulk acoustic wave filter; respectively forming bump structures in the plurality of electrode connection regions through the plurality of openings; and encapsulating the bulk acoustic wave filter on a substrate based on the plurality of bump structures to obtain a bulk acoustic wave device.

[0058] Figure 1 Schematically shows a flowchart of a method for manufacturing a bulk acoustic wave device according to an embodiment of the present disclosure.

[0059] As Figure 1 shown, the method includes operations S110 to S140.

[0060] In operation S110, a bulk acoustic wave filter is formed on a silicon-based substrate.

[0061] In operation S120, a protective layer is deposited on the front and back surfaces of the bulk acoustic wave filter.

[0062] In operation S130, a plurality of openings are etched in the protective layer based on a plurality of electrode connection regions included in the surface of the bulk acoustic wave filter.

[0063] In operation S140, the bulk acoustic wave filter is encapsulated based on the plurality of openings to obtain a bulk acoustic wave device.

[0064] According to an embodiment of the present disclosure, a bulk acoustic wave filter can be formed through the following steps. First, an appropriate silicon-based substrate is selected and surface treatment such as cleaning and removing surface impurities is performed. Using a suitable deposition technique, a bottom electrode layer is deposited on the silicon-based substrate. Using photolithography technology and etching process, the positions and shapes of the electrode connection regions are defined on the bottom electrode layer. An upper electrode layer is deposited on the oscillation layer. The upper electrode is usually similar to the bottom electrode and sandwiches a piezoelectric layer with the bottom electrode to generate a bulk acoustic wave filtering effect, thereby obtaining a bulk acoustic wave filter.

[0065] According to an embodiment of the present disclosure, the purpose of depositing a protective layer on the surface of the bulk acoustic wave filter is to prevent the filter from being affected by the external environment, such as humidity, oxidation, corrosion, etc., thereby affecting the function and performance of the filter. Common protective layer materials include silicon oxide, silicon nitride, aluminum oxide, etc. Atomic Layer Deposition (ALD) technology can be used for deposition. ALD can achieve atomic-level control of the film thickness and composition. The deposited film has a very uniform thickness and composition, and various types of materials can be deposited. Therefore, a uniform and dense protective layer can be obtained by using ALD technology.

[0066] According to an embodiment of the present disclosure, a substrate suitable for packaging is designed according to the size and connection requirements of the bulk acoustic wave filter. When ensuring the correct connection between the bulk acoustic wave filter and the circuit on the substrate, the bulk acoustic wave filter is fixed at the corresponding position on the substrate by SMT or FCT, and the bulk acoustic wave filter fixed on the substrate is encapsulated by a film covering technology to obtain a bulk acoustic wave device.

[0067] According to an embodiment of the present disclosure, a protective layer is formed on the surface of the bulk acoustic wave filter, and the protective layer is used to prevent the bulk acoustic wave filter from being eroded by water vapor in the operating environment. Then, openings are formed by etching the protective layer, and the electrodes exposed by the openings are processed to form bump structures. The filter device is connected to the substrate using SMT or FCT, and the encapsulation of the bulk acoustic wave filter is completed by a film covering technology to obtain a bulk acoustic wave device. The preparation method of this bulk acoustic wave device does not require wafer-level packaging, and does not require the use of expensive metals as sealing metal rings. A simpler process flow can be used to generate the protective layer and the encapsulation structure, reducing the complexity of the process and the cost of the materials used, thereby improving the yield rate of preparing the bulk acoustic wave device and effectively reducing the production cost of preparing the bulk acoustic wave device.

[0068] According to an embodiment of the present disclosure, a bulk acoustic wave filter is formed on a silicon-based substrate, including: etching a cavity structure on the silicon-based substrate; filling a sacrificial layer material in the cavity structure to obtain a sacrificial layer; sequentially forming a seed layer, a lower electrode layer, a piezoelectric layer, an upper electrode layer, a passivation layer, and an electrode connection layer from the surface of the sacrificial layer upward; and releasing the sacrificial layer material through a release structure to obtain a bulk acoustic wave filter.

[0069] Figure 2 A schematic diagram of an FBAR type bulk acoustic wave filter according to an embodiment of the present disclosure is schematically shown.

[0070] As Figure 2 shown, a pit, that is, a cavity structure 21, is etched on the silicon-based substrate. A sacrificial layer material is filled in the pit, and the filled sacrificial layer material can be polished flat by CMP. Then, a seed layer 22, a lower electrode layer 23, a piezoelectric layer 24, an upper electrode layer 25, a passivation layer 26, and an electrode connection layer 27 are sequentially formed, and then the sacrificial layer material is released to form a cavity, thereby forming a bulk acoustic wave filter.

[0071] According to an embodiment of the present disclosure, a sacrificial layer material can be filled into a cavity structure on a substrate. The sacrificial layer material can be related to the sacrificial layer removal liquid selected when removing the sacrificial layer material by wet etching, that is, the sacrificial layer material can be selected as a material that easily reacts with the sacrificial layer removal liquid and leaves no solid residue after the reaction. For example, the sacrificial layer removal liquid can be selected as HF (hydrofluoric acid), BOE (Buffered Oxide etchant), etc. Correspondingly, the sacrificial layer material can be selected as a material that easily reacts with HF, BOE, etc. For example, SiO2 (silicon dioxide), PSG (Phospho-Silicate Glass), BPSG (Boro-Phospho-Silicate Glass), etc.

[0072] According to an embodiment of the present disclosure, in the process of forming the lower electrode layer and the upper electrode layer, a metal material with low acoustic loss can be used as the plating material, such as Mo (molybdenum), Al (aluminum), W (tungsten), etc. That is, the material of the lower electrode layer or the upper electrode layer is Mo, Al, or W. In the process of forming the piezoelectric layer, a material with low acoustic loss can be used as the plating material, such as AlN, PZT (lead zirconate titanate), ZnO (zinc oxide), etc. That is, the piezoelectric layer material is AlN, PZT, or ZnO. Optionally, the piezoelectric layer material can also be a material doped with other rare metals, which is not limited herein.

[0073] Figure 3 A schematic diagram of an SMR type bulk acoustic wave filter according to an embodiment of the present disclosure is schematically shown.

[0074] As Figure 3 shown, the method for manufacturing a bulk acoustic wave device according to the present disclosure is applicable not only to FBAR type bulk acoustic wave filters but also to SMR type bulk acoustic wave filters. The SMR type bulk acoustic wave filter includes an impedance layer 11, wherein the impedance layer 11 is formed by alternately stacking a high-impedance layer and a low-impedance layer. Then, a seed layer 22, a lower electrode layer 23, a piezoelectric layer 24, an upper electrode layer 25, a passivation layer 26, and an electrode connection layer 27 are formed upward in sequence.

[0075] According to an embodiment of the present disclosure, in the process of forming the passivation layer, a material with low acoustic loss and non-reactive with HF solution can be selected, such as AlN (aluminum nitride). The passivation layer can simultaneously serve as a frequency modulation layer, and the thickness of the passivation layer can be set according to the actual product requirements, which is not limited herein.

[0076] According to an embodiment of the present disclosure, a protective layer is deposited and formed on the surface of the bulk acoustic wave filter, including: forming a protective layer on the surface of the bulk acoustic wave filter by an atomic layer deposition method, wherein the thickness of the protective layer is between 1 nm and 100 nm.

[0077] According to an embodiment of the present disclosure, a protective layer is deposited on the front and back surfaces of the bulk acoustic wave filter, including: depositing a protective layer on the front and back surfaces of the bulk acoustic wave filter and the inner surface of the cavity structure.

[0078] Figure 4 A schematic diagram of a bulk acoustic wave filter with a protective layer according to an embodiment of the present disclosure is schematically shown.

[0079] As Figure 4 shown, on the front and back surfaces of the bulk acoustic wave filter and the inner surface of the cavity structure, a protective layer 28 is formed by ALD. The protective layer 28 can be a single layer or multiple layers of materials. The material selection includes alumina AL2O3, silicon dioxide SiO2, silicon nitride Si3N4, etc. which are insulating and have good waterproof properties; for the protective layer formed by ALD, considering the time cost and subsequent frequency modulation, the thickness can be between 1 nm and 100 nm. Al2O3 can be formed at a temperature of 100 - 300 °C, and SiO2 and Si3N4 can be formed in an environment of 200 - 360 °C. It is verified by experiments that the waterproof properties of Si3N4 and SiO2 are better than other materials in a high-temperature and high-humidity environment. Under an accelerated high-temperature and high-humidity environment (130 °C, 85% RH, 33.3 psia, 96 hrs), the frequency change of SiO2 is within 0.5 M, while the frequency change of AlN is about 12 M.

[0080] According to an embodiment of the present disclosure, based on a plurality of electrode connection regions included in the front surface of the bulk acoustic wave filter, a plurality of openings are etched in the protective layer, including: coating a photoresist on the surface of the protective layer based on the respective positions of the plurality of electrode connection regions, and performing exposure and development; and etching the protective layer coated with the photoresist to form a plurality of openings in the protective layer.

[0081] According to an embodiment of the present disclosure, by selecting an appropriate material to make the protective layer, and performing surface cleaning and treatment, the surface of the protective layer is coated with a photoresist. During the coating process, the coating thickness and uniformity need to be controlled to ensure the final opening quality. By means of exposure and development, the photoresist in the electrode connection region is removed. This will form many small holes, namely the so-called openings, in the protective layer. The protective layer is etched using chemical or physical methods to form the openings. This can be achieved by wet etching or dry etching, specifically depending on the materials used and the process requirements. After the etching is completed, the protective layer needs to be cleaned and dried to remove residual chemical substances and moisture, ensuring the surface finish and dryness of the openings.

[0082] According to an embodiment of the present disclosure, forming a plurality of openings on a protective layer can be used to connect the electrodes of a bulk acoustic wave filter. This method can achieve high-precision opening manufacturing while ensuring the accuracy of the opening spacing and position. It can also avoid material interaction and corrosion in the electrode connection area, thereby improving the reliability and stability of the connection.

[0083] According to an embodiment of the present disclosure, based on a plurality of electrode connection areas included in the surface of a bulk acoustic wave filter, etching a plurality of openings on the protective layer includes: disposing a steel mesh between 1 μm and 50 μm above the protective layer, where the steel mesh includes a plurality of hollowed-out areas, and the plurality of hollowed-out areas respectively correspond to the plurality of electrode connection areas; performing dry etching on the protective layer through the steel mesh to form a plurality of openings on the protective layer; and removing the steel mesh.

[0084] Figure 5 Schematically shows a schematic diagram of forming an opening by etching through a steel mesh according to an embodiment of the present disclosure.

[0085] As Figure 5 shown, place a steel mesh 30 above the protective layer. The steel mesh 30 should have a plurality of hollowed-out areas, and these areas respectively correspond to the plurality of electrode connection areas. The function of the steel mesh 30 is to control the position and shape of the dry etching. Perform dry etching on the protective layer through the steel mesh 30. Dry etching is a high-precision etching method that uses an ion beam to remove part of the material of the protective layer to form an opening. The ion beam can achieve precise control of the opening position and size by controlling the layout of the steel mesh 30 and the parameters of the ion beam.

[0086] According to an embodiment of the present disclosure, the ALD material needs to be removed from the electrode connection area for electrical connection. Place a steel mesh above the bulk acoustic wave filter and bombard the whole surface by ion beam etching in dry etching. The steel mesh is designed to only open the electrode connection positions. Therefore, after etching is completed, only the ALD material at the electrode connection positions is removed.

[0087] According to an embodiment of the present disclosure, if the steel mesh is too close to the surface of the protective layer, it may damage the device performance. If the steel mesh is too far from the surface of the protective layer, dry etching will etch into other areas through the opening positions of the steel mesh. Therefore, the distance between the steel mesh position and the surface of the protective layer can be set to 1 μm to 50 μm.

[0088] According to an embodiment of the present disclosure, in this embodiment, there is no need to perform WLP packaging. After forming the bulk acoustic wave filter, a protective layer is formed on the passivation layer by ALD. The protective layer can be one or more layers of waterproof materials, and the materials can be insulating and waterproof materials such as aluminum oxide AL2O3, silicon dioxide SiO2, and silicon nitride Si3N4.

[0089] Since the ALD process is a blanket process and electrical connection is required in the electrode connection area, the ALD material at this position needs to be etched away. However, due to the cavity structure of the bulk acoustic wave filter, when using the traditional photolithography method, the photoresist may enter the cavity, which may cause the photoresist to be unable to be completely removed. Therefore, the present invention can adopt the method of stencil etching, using the stencil to block the non-etched parts, and then using the ion beam etching method in dry etching to bombard the electrode connection position, that is, the position where the stencil is opened, to complete the etching of the ALD material at the electrode connection position.

[0090] Figure 6 Schematically shows a schematic diagram of a bulk acoustic wave filter after etching according to an embodiment of the present disclosure.

[0091] As Figure 6 shown, only the protective layer formed by deposition in the electrode connection area is removed, and the other parts of the bulk acoustic wave filter still have the protective layer.

[0092] According to an embodiment of the present disclosure, the method for manufacturing a bulk acoustic wave device further includes: before forming bump structures in multiple electrode connection areas respectively through multiple openings, performing a frequency response test on the bulk acoustic wave filter to obtain the resonant or anti-resonant frequency of the device; and based on the deviation between the device frequency and the expected device frequency, performing an etching process on the protective layer, or depositing a new protective layer on the surface of the bulk acoustic wave filter.

[0093] According to an embodiment of the present disclosure, after the electrode connection position is opened, the device can be tested again to confirm whether there is a deviation between the device frequency and the expected device frequency. If the deviation is within an acceptable range, the bulk acoustic wave filter can be directly coated with a film to protect the surface of the device and improve its stability and durability. If the deviation exceeds the acceptable range, if the deviation is low, the etched opening can be slightly adjusted or trimmed. If the deviation between the frequencies is high, the etching process can be used to remove part of the protective layer, or a new protective layer can be deposited on the surface of the device to adjust the frequency characteristics of the device and protect its performance.

[0094] According to an embodiment of the present disclosure, if the deviation is within an acceptable range, the bulk acoustic wave filter can be directly coated with a film to protect the surface of the device and improve its stability and durability. If the deviation exceeds the acceptable range, the protective layer needs to be further processed. The etching process can be used to remove part of the protective layer, or a new protective layer can be deposited on the surface of the device to adjust the frequency characteristics of the device and protect its performance.

[0095] According to an embodiment of the present disclosure, frequency modulation processing can also be performed on the passivation layer through frequency testing, and the specific process used for the frequency modulation processing is not limited herein. Optionally, dry etching can be used to adjust the thickness of the passivation layer of the bulk acoustic wave filter to perform frequency modulation processing on the bulk acoustic wave filter. Using dry etching to adjust the thickness of the passivation layer of the bulk acoustic wave filter may be to use Ar (argon) ions to bombard the surface material of the passivation layer to break the chemical bonds between the surface material molecules of the passivation layer, thereby removing at least part of the surface material of the passivation layer to adjust the device frequency of the bulk acoustic wave filter.

[0096] According to an embodiment of the present disclosure, encapsulation processing is performed on the bulk acoustic wave filter based on a plurality of openings to obtain a bulk acoustic wave device, including: respectively forming bump structures in a plurality of electrode connection regions through the plurality of openings; and encapsulating the bulk acoustic wave filter on a substrate based on the plurality of bump structures to obtain a bulk acoustic wave device.

[0097] According to an embodiment of the present disclosure, a plurality of openings are etched and formed on the surface of the bulk acoustic wave filter for opening a path corresponding to the electrode connection region on the protective layer to facilitate the connection and testing of the electrodes. These openings can be formed by a dry etching process and realized by means of photolithography or stencil etching. The prepared openings can accurately form a path corresponding to the electrode connection region on the protective layer to facilitate subsequent electrode connection and testing work. This processing method helps to ensure the reliability of the electrode connection and the stability of the filter performance.

[0098] According to an embodiment of the present disclosure, a bump structure can be formed on the bulk acoustic wave filter below the opening by filling or depositing metal or other conductive materials in the opening. Among them, a bump structure can be formed by implanting metal balls in the electrode connection region, and the implanted metal balls can be tin balls or gold balls. Among them, a bump structure can also be formed in the electrode connection region by means of stencil printing, or a bump structure can be prepared by implanting tin balls in the electrical connection region. According to the size and connection requirements of the bulk acoustic wave filter, a substrate suitable for encapsulation is designed. Under the condition of ensuring the correct connection between the bulk acoustic wave filter and the circuit on the substrate, the bump structure on the bulk acoustic wave filter is fixed at the corresponding substrate position by SMT or FCT method to form a bulk acoustic wave device. According to an embodiment of the present disclosure, encapsulating the bulk acoustic wave filter on a substrate based on a plurality of bump structures to obtain a bulk acoustic wave device includes: cutting a silicon-based substrate based on the position of the bulk acoustic wave filter to obtain grains related to the bulk acoustic wave filter; mounting and soldering the grains on the substrate by surface mount technology or flip-chip technology based on the plurality of bump structures to obtain an initial bulk acoustic wave device; and performing a film covering process on the initial bulk acoustic wave device to obtain a bulk acoustic wave device. Among them, the surface of the electrode connection layer includes a plurality of electrode connection regions.

[0099] Figure 7A schematic diagram showing the ball mounting of a bulk acoustic wave filter according to an embodiment of the present disclosure is schematically shown.

[0100] As Figure 7 shown, bump structures are formed in the electrode connection area. The materials of the bump structures can be tin balls and gold balls. The tin balls can be formed by stencil printing or ball mounting methods, and the gold balls can be formed by wire bonding processes or thermocompression ultrasonic methods. The electrode connection layer for tin ball mounting is Al or Cu (copper), and the electrode connection layer for gold ball mounting is selected as Au (gold) or Al.

[0101] Figure 8 A schematic diagram showing an initial bulk acoustic wave device according to an embodiment of the present disclosure is schematically shown.

[0102] As Figure 8 shown, the wafer with the bump structures implanted is cut into individual dies. Among them, the wafer can be cut by laser cutting and water jet cutting methods. The individual dies obtained by cutting are mounted on the substrate through SMT technology or FCT technology.

[0103] Figure 9 A schematic diagram showing a bulk acoustic wave device according to an embodiment of the present disclosure is schematically shown.

[0104] As Figure 9 shown, the bulk acoustic wave filter is wrapped and sealed with an epoxy resin film material to obtain the packaging structure of the initial bulk acoustic wave device, that is, the bulk acoustic wave device.

[0105] According to an embodiment of the present disclosure, by using a bare initial bulk acoustic wave device inverted on the substrate and then covered with a film for packaging, the manufacturing cost of wafer-level packaging can be saved, the chip thickness and size are reduced, the miniaturization degree of the filter is improved, the yield of a single wafer is increased, the unit cost of the product is reduced, and at the same time, the reliability ability is greatly improved.

[0106] According to an embodiment of the present disclosure, it further includes a bulk acoustic wave device prepared by the method for preparing a bulk acoustic wave device according to any one of the above.

[0107] Those skilled in the art can understand that the features recited in the various embodiments and / or claims of the present disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly recited in the present disclosure. In particular, without departing from the spirit and teachings of the present disclosure, the features recited in the various embodiments and / or claims of the present disclosure can be combined and / or combined in various ways. All such combinations and / or combinations fall within the scope of the present disclosure.

[0108] The embodiments of the present disclosure have been described above. However, these embodiments are merely for illustrative purposes and are not intended to limit the scope of the present disclosure. Although the embodiments have been described separately above, this does not mean that the measures in each embodiment cannot be used advantageously in combination. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art can make various substitutions and modifications, and all such substitutions and modifications should fall within the scope of the present disclosure.

Claims

1. A method for fabricating a bulk acoustic wave device, comprising: Forming a bulk acoustic wave filter on a silicon-based substrate; Depositing a protective layer on the front and back surfaces of the bulk acoustic wave filter; Etching a plurality of openings in the protective layer based on a plurality of electrode connection regions included on the surface of the bulk acoustic wave filter; And Performing a packaging process on the bulk acoustic wave filter based on the plurality of openings to obtain a bulk acoustic wave device.

2. The method according to claim 1, wherein, The etching a plurality of openings in the protective layer based on a plurality of electrode connection regions included on the surface of the bulk acoustic wave filter includes: Coating a photoresist on the surface of the protective layer based on the positions of the plurality of electrode connection regions, and performing exposure and development; and Etching the protective layer coated with the photoresist to form a plurality of openings in the protective layer.

3. The method according to claim 1, wherein The etching a plurality of openings in the protective layer based on a plurality of electrode connection regions included on the surface of the bulk acoustic wave filter includes: Providing a stencil between 1 μm and 50 μm above the protective layer, wherein the stencil includes a plurality of hollowed-out regions, and the plurality of hollowed-out regions respectively correspond to the plurality of electrode connection regions; Performing dry etching on the protective layer through the stencil to form the plurality of openings in the protective layer; and Removing the stencil.

4. The method according to claim 1, wherein, The performing a packaging process on the bulk acoustic wave filter based on the plurality of openings to obtain a bulk acoustic wave device includes: Respectively forming bump structures in the plurality of electrode connection regions through the plurality of openings; and Based on the plurality of bump structures, packaging the bulk acoustic wave filter on a substrate to obtain the bulk acoustic wave device.

5. The method according to claim 4, further comprising: Before respectively forming bump structures in the plurality of electrode connection regions through the plurality of openings, performing a frequency response test on the bulk acoustic wave filter to obtain a device resonance or anti-resonance frequency; and Based on the deviation between the device frequency and the expected device frequency, etching the protective layer, or depositing a new protective layer on the surface of the bulk acoustic wave filter.

6. The method according to claim 4, wherein, The packaging the bulk acoustic wave filter on a substrate based on the plurality of bump structures to obtain a bulk acoustic wave device includes: Cutting the silicon-based substrate based on the position of the bulk acoustic wave filter to obtain a die related to the bulk acoustic wave filter; Based on the plurality of bump structures, mounting and soldering the die on the substrate through surface mount technology or flip-chip technology to obtain an initial bulk acoustic wave device; and Performing a film covering process on the initial bulk acoustic wave device to obtain the bulk acoustic wave device.

7. The method according to claim 1, wherein The forming a bulk acoustic wave filter on a silicon-based substrate includes: Etching a cavity structure in the silicon-based substrate; Filling a sacrificial layer material in the cavity structure to obtain a sacrificial layer; Sequentially forming a seed layer, a lower electrode layer, a piezoelectric layer, an upper electrode layer, a passivation layer, and an electrode connection layer upward from the surface of the sacrificial layer, wherein the surface of the electrode connection layer includes the plurality of electrode connection regions; and Releasing the sacrificial layer material through a release structure to obtain the bulk acoustic wave filter.

8. The method according to claim 7, wherein, Depositing and forming a protective layer on the front and back surfaces of the surface acoustic wave filter includes: Depositing and forming the protective layer on the front and back surfaces of the surface acoustic wave filter and on the inner surface of the cavity structure.

9. The method according to claim 1, wherein Depositing and forming a protective layer on the front surface of the surface acoustic wave filter includes: Using atomic layer deposition method to form the protective layer on the front surface of the surface acoustic wave filter, wherein the thickness of the protective layer is between 1 nm and 100 nm, and the material of the protective layer is Al2O3, SiO2 or Si3N4.

10. A surface acoustic wave device prepared by using the method for preparing a surface acoustic wave device according to any one of claims 1 to 9.

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