Method for manufacturing bulk acoustic wave resonator and applications thereof

Abstract

This disclosure provides a method for manufacturing a bulk acoustic wave resonator, comprising: providing a carrier; etching a first etched portion in the carrier; sequentially conformally depositing a filler material and a lower electrode material layer in the first etched portion, wherein the thickness of the filler material is greater than or equal to the height required for normal operation of the bulk acoustic wave resonator; removing the lower electrode material layer and the filler material from the upper surface of the carrier by a planarization process, forming a filler layer and a lower electrode in the cavity of the first etched portion, wherein the upper surface of the lower electrode, the upper surface of the filler layer, and the upper surface of the carrier are on the same plane; forming a piezoelectric layer on the carrier, wherein the lower surface of the piezoelectric layer, the upper surface of the carrier, the upper surface of the filler layer, and the upper surface of the lower electrode are on the same plane; wherein the height of the first etched portion is at least greater than the sum of the over-grinding amount of the carrier set in the planarization process, the flatness range of the planarization process, the thickness of the lower electrode, and the height required for normal operation of the bulk acoustic wave resonator.

Description

Technical Field

[0001] This disclosure relates to the field of electronics, and more specifically, to a method for manufacturing a bulk acoustic resonator and its application. Background Technology

[0002] See Figure 1 , Figure 1 This is a schematic diagram of the structure of an existing thin-film bulk acoustic resonator (FBAR). Figure 1 As shown, the thin-film bulk acoustic resonator includes a carrier 101, a cavity 102 formed in the carrier 101, a lower electrode 103, an upper electrode 105, and a piezoelectric layer 104 sandwiched between the upper and lower electrodes (i.e., the lower electrode 103 and the upper electrode 105), wherein the upper and lower electrodes and the piezoelectric layer form a "sandwich" structure, and a protective layer 106 is further formed on the upper electrode 105.

[0003] In the process of fabricating a thin-film bulk acoustic resonator, a cavity 102 is usually formed in the carrier 101 first, and then a sacrificial material is filled into the cavity 102. When filling the sacrificial material, the sacrificial material needs to cover the entire upper surface of the carrier 101. After filling, a planarization process such as chemical-mechanical polishing (CMP) is performed to remove the sacrificial material on the upper surface of the carrier 101 outside the cavity 102, thereby providing a planarized surface for the formation of the lower electrode 103.

[0004] Then, the lower electrode 103 is formed on the upper surface of the carrier 101, at least covering the upper surface of the cavity 102 filled with sacrificial material. The piezoelectric layer 104 is further formed on the lower electrode 103. Due to the abrupt inflection point in the contact area between the piezoelectric layer 104 and the lower electrode 103, stress concentration occurs, which can easily cause cracks in the piezoelectric layer 104 in this area due to stress, thereby affecting the reliability of the thin-film bulk acoustic resonator.

[0005] To address the aforementioned technical problems, in the prior art, a tilted structure with a very small tilt angle is typically etched at the edge of the lower electrode 103 during fabrication. However, the tilted structure at the edge of the lower electrode 103 is usually formed by photolithography and etching. On the one hand, the very small tilt angle places high demands on the photolithography and etching processes; on the other hand, the upper surface of the tilted structure is of relatively poor quality due to the bombardment of plasma during the etching process. Consequently, the quality of the piezoelectric layer 104 grown on the upper surface of the tilted structure is also poor. Furthermore, abrupt inflection points inevitably still exist on the tilted structure, leading to stress concentration at the junction of the piezoelectric layer 104 and the lower electrode 103. This results in an increase in parasitic modes in the thin-film bulk acoustic resonator and a decrease in the electromechanical coupling coefficient of the thin-film bulk acoustic resonator. Summary of the Invention

[0006] This disclosure addresses the aforementioned technical problems by designing a fabrication process for a thin-film bulk acoustic resonator, which can alleviate or solve at least one aspect of the aforementioned technical problems.

[0007] A brief overview of this disclosure will be given below to provide a basic understanding of certain aspects of it. It should be understood that this overview is not an exhaustive summary of this disclosure. It is not intended to identify key or essential parts of this disclosure, nor is it intended to limit the scope of this disclosure. Its purpose is merely to present certain concepts in a simplified form as a prelude to the more detailed description that follows.

[0008] According to one aspect of this disclosure, a method for manufacturing a bulk acoustic wave resonator is provided, comprising: providing a carrier; etching a first etched portion in the carrier; sequentially conformally depositing a filler material and a lower electrode material layer in the first etched portion, wherein the thickness of the filler material is greater than or equal to the height required for normal operation of the bulk acoustic wave resonator; removing the lower electrode material layer and the filler material from the upper surface of the carrier by a planarization process, forming a filler layer and a lower electrode in the cavity of the first etched portion, wherein the upper surface of the lower electrode, the upper surface of the filler layer, and the upper surface of the carrier are in the same plane; forming a piezoelectric layer on the carrier, wherein the lower surface of the piezoelectric layer, the upper surface of the carrier, the upper surface of the filler layer, and the upper surface of the lower electrode are in the same plane; wherein the height of the first etched portion is at least greater than the sum of the over-grinding amount of the carrier set in the planarization process, the flatness range of the planarization process, the thickness of the lower electrode, and the height required for normal operation of the bulk acoustic wave resonator.

[0009] Furthermore, a seed layer is formed within the first etched portion before the lower electrode is formed.

[0010] Furthermore, the height of the first etched portion is at least greater than the sum of the over-grinding amount of the carrier, the flatness range of the planarization process, the thickness of the seed layer, the thickness of the lower electrode, and the height required for the normal operation of the bulk acoustic resonator, as set in the planarization process.

[0011] Furthermore, a passivation layer is formed within the first etched portion before the seed layer is formed.

[0012] Furthermore, the height of the first etched portion is at least greater than the sum of the over-grinding amount of the carrier, the flatness range of the planarization process, the thickness of the passivation layer, the thickness of the seed layer, the thickness of the lower electrode, and the height required for the normal operation of the bulk acoustic wave resonator.

[0013] Furthermore, the angle between each sidewall of the first etched portion and the bottom surface of the first etched portion is 90-160°.

[0014] Furthermore, the carrier is a single substrate or a composite structure consisting of a substrate and a dielectric layer.

[0015] Furthermore, the interval between the projection profile of the lower electrode on the carrier and the projection profile of the minimum cross-section of the first etched portion on the carrier is at least less than or equal to the thickness of the filling material.

[0016] Furthermore, a filling layer is formed within the first etched portion before forming the lower electrode, the seed layer, or the passivation layer.

[0017] Furthermore, an upper electrode is formed on the piezoelectric layer; the projection profile of the upper electrode on the carrier falls within the projection profile of the smallest cross-section of the first etched portion on the carrier; after the upper electrode is formed, the filler layer in the first etched portion is removed.

[0018] According to another aspect of this disclosure, a bulk acoustic wave resonator is provided, comprising: a carrier having a cavity formed therein; a lower electrode formed within the cavity, the upper surface of the lower electrode being in the same plane as the upper surface of the carrier; and a piezoelectric layer formed on the carrier, the lower surface of the piezoelectric layer, the upper surface of the carrier, and the upper surface of the lower electrode being in the same plane; wherein the height of the cavity is at least greater than or equal to the sum of the thickness of the lower electrode and the height required for normal operation of the bulk acoustic wave resonator; and the interval between the projected profile of the lower electrode on the carrier and the projected profile of the minimum cross-section of the cavity on the carrier is less than or equal to the height required for normal operation of the bulk acoustic wave resonator.

[0019] Furthermore, the height required for the bulk acoustic resonator to operate normally is greater than or equal to 0.5 μm; the thickness of the lower electrode is between 0.1 and 0.5 μm.

[0020] Furthermore, it also has a seed crystal layer located within the cavity, surrounding the side and lower surfaces of the lower electrode. The interval between the projected profile of the seed crystal layer on the carrier and the projected profile of the minimum cross-section of the cavity on the carrier is less than or equal to the sum of the height required for the normal operation of the bulk acoustic resonator and the thickness of the seed crystal layer.

[0021] Furthermore, the height of the cavity is at least greater than or equal to the sum of the thickness of the lower electrode, the thickness of the seed layer, and the height required for the normal operation of the bulk acoustic resonator.

[0022] Furthermore, it also has a passivation layer located within the cavity, surrounding the side and lower surfaces of the seed crystal layer. The interval between the projection profile of the passivation layer on the carrier and the projection profile of the minimum cross-sectional area of ​​the cavity on the carrier is less than or equal to the sum of the height required for normal operation of the bulk acoustic resonator, the thickness of the seed crystal layer, and the thickness of the passivation layer.

[0023] Furthermore, the height of the cavity is at least greater than or equal to the thickness of the lower electrode, the thickness of the seed crystal layer, the thickness of the passivation layer, and the sum of the thickness required for the normal operation of the bulk acoustic resonator.

[0024] Furthermore, the angle between each sidewall of the cavity and the bottom surface of the cavity is 90-160°.

[0025] Furthermore, the carrier is a single substrate or a composite structure consisting of a substrate and a dielectric layer.

[0026] According to another aspect of this disclosure, an electronic device is provided, characterized in that it includes a bulk acoustic resonator as described in any of the preceding claims.

[0027] According to another aspect of this disclosure, an electronic device is provided, comprising the bulk acoustic resonator described in any of the preceding claims.

[0028] The disclosed solution can help achieve at least one of the following effects: it can simplify the process, avoid stress concentration problems at the contact part between the piezoelectric layer and the lower electrode, facilitate the subsequent growth of piezoelectric thin films, improve the reliability of thin film bulk acoustic resonators, reduce parasitic modes of thin film bulk acoustic resonators, avoid reducing the electromechanical coupling coefficient of thin film bulk acoustic resonators, and improve the product yield of thin film bulk acoustic resonators. Attached Figure Description

[0029] The specific details of this disclosure are described below with reference to the accompanying drawings, which will facilitate a more readily understanding of the above and other objects, features, and advantages of this disclosure. The drawings are merely for illustrating the principles of this disclosure. The dimensions and relative positions of the elements are not necessarily drawn to scale in the drawings.

[0030] Figure 1 A schematic diagram of an existing thin-film bulk acoustic resonator is shown.

[0031] Figures 2a-2b This diagram illustrates the structure of a thin-film bulk acoustic resonator provided in a specific embodiment of the present disclosure.

[0032] Figures 3a-8b This is a schematic diagram of the manufacturing process of the thin-film bulk acoustic resonator structure provided in the embodiments of this disclosure. Detailed Implementation

[0033] Exemplary disclosures of this disclosure will be described below with reference to the accompanying drawings. For clarity and brevity, not all features implementing this disclosure are described in the specification. However, it should be understood that many disclosure-specific decisions can be made in developing any such implementation of this disclosure to achieve the developer’s specific goals, and these decisions may vary depending on the specific disclosure.

[0034] It should also be noted that, in order to avoid obscuring this disclosure with unnecessary details, only the device structure closely related to the scheme according to this disclosure is shown in the accompanying drawings, while other details that are not closely related to this disclosure are omitted.

[0035] It should be understood that this disclosure is not limited to the described embodiments by virtue of the following description with reference to the accompanying drawings. Throughout this document, features may be substituted or borrowed between different embodiments where feasible, and one or more features may be omitted in one embodiment. It should be understood that the manufacturing steps of this disclosure are exemplary in the embodiments, and the order of the steps may be adjusted.

[0036] See Figures 2a-2b , Figures 2a-2b A schematic diagram of the structure of a thin-film bulk acoustic resonator provided in a specific embodiment of this disclosure is shown, wherein the same reference numerals denote the same components.

[0037] like Figures 2a-2b As shown, the thin-film bulk acoustic resonator includes: a carrier 1000, in which a cavity 1100 is formed. Those skilled in the art will understand that the carrier 1000 can, exemplarily, be made of a substrate, such as silicon (Si), gallium arsenide (GaAs), indium phosphide (InP), glass, sapphire, or aluminum oxide. 、 Materials compatible with semiconductor processes, such as SiC and POI; or, the carrier 1000 may be a composite structure formed on the substrate with a dielectric layer, which may be a single layer or multiple layers, and the dielectric layer may be made of materials such as silicon dioxide (SiO2), silicon nitride (Si3N4), silicon dioxide / silicon nitride / silicon dioxide (ONO), aluminum oxide (Al2O3), etc.

[0038] Furthermore, the cavity 1100 can be formed on the carrier 1000 by etching. When the carrier 1000 is a composite, the cavity 1100 can be formed in the substrate, in the dielectric layer, or simultaneously in the substrate and the dielectric layer.

[0039] The cavity 1100 in the carrier 1000 has sides and a bottom, such as Figure 2aAs shown, in one specific embodiment, the angle between each side of cavity 1100 and the bottom of cavity 1100 is, for example, approximately 90 degrees. It is understood that when the angle between the side of cavity 1100 and the bottom of cavity 1100 is set to 90 degrees, a perfect 90 degrees cannot usually be achieved due to process and measurement tolerances. Here, "approximately 90 degrees" represents 90 degrees as an ideal value, covering the 90-degree tolerance range caused by process and measurement. In this document, "approximately" always indicates a situation that covers the tolerance range caused by process and measurement. The upper surface of cavity 1100 can be a regular or irregular polygonal shape, such as a quadrilateral, an irregular pentagon, a triangle, an octagon, etc.

[0040] In another specific implementation, such as Figure 2b As shown, the angle between each side surface of cavity 1100 and the bottom surface of cavity 1100 is greater than 90 degrees and less than or equal to 160 degrees; this is more conducive to the subsequent growth of the lower electrode / piezoelectric layer / upper electrode. Furthermore, the angles formed by each side surface of cavity 1100 and the bottom surface of cavity 1100 may be the same or different.

[0041] Furthermore, it can be understood that the slope of each side of the cavity 1100 can be the same slope, a gradually changing slope, or a non-gradual slope, and the shape of each side of the cavity 1100 can be stepped or curved.

[0042] Continue reading Figures 2a-2b A lower electrode 2000 is formed on the carrier 1000, completely located within the cavity 1100. The lower electrode 2000 can be a single layer or multiple layers, and can be formed of one or more conductive materials, such as various metals compatible with semiconductor processes, including tungsten (W), molybdenum (Mo), iridium (Ir), aluminum (Al), platinum (Pt), ruthenium (Ru), niobium (Nb), or hafnium (Hf). The upper surface of the lower electrode 2000 is on the same plane as the upper surface of the carrier 1000. Furthermore, those skilled in the art should understand that the shape of the lower electrode 2000 can be arbitrary, and the present invention does not further limit the shape of the lower electrode 2000. For example, the projected outline of the lower electrode 2000 on the surface of the carrier 1000 can be an irregular shape or a regular shape, such as a triangle, rectangle, pentagon, hexagon, octagon, or other regular polygon.

[0043] Furthermore, the interval between the projected profile of the lower electrode 2000 on the surface of the carrier 1000 and the projected profile of the minimum cross-section of the cavity 1100 on the surface of the carrier 1000 has a height less than or equal to that required for the normal operation of the bulk acoustic resonator.

[0044] Then, a piezoelectric layer 3000 is formed on the lower electrode 2000. The piezoelectric layer 3000 can be formed from any piezoelectric material compatible with semiconductor processes, such as aluminum nitride (AlN), doped aluminum nitride, or zirconate titanate (PZT). The lower surface of the piezoelectric layer 3000 is in the same plane as the upper surface of the carrier 1000 and the upper surface of the lower electrode 2000.

[0045] In this disclosure, the lower electrode 2000 is completely disposed within the cavity 1100, and the lower surface of the piezoelectric layer 3000, the upper surface of the carrier 1000, and the upper surface of the lower electrode 2000 are on the same plane. This results in a flat surface at the contact portion between the piezoelectric layer 3000 and the lower electrode 2000, without any tilted structure. Therefore, the thin film crystal orientation of the piezoelectric layer 3000 can be improved, thereby enhancing the device performance of the thin-film bulk acoustic resonator.

[0046] Then, an upper electrode 4000 is formed on the piezoelectric layer 3000. The upper electrode 4000 can be formed of one or more conductive materials, such as various metals compatible with semiconductor processes, including tungsten (W), molybdenum (Mo), iridium (Ir), aluminum (Al), platinum (Pt), ruthenium (Ru), niobium (Nb), or hafnium (Hf). The materials of the upper electrode and the lower electrode can be the same or different. Furthermore, those skilled in the art should understand that the shape of the upper electrode 4000 can be arbitrary, and the shape of the upper electrode 4000 is not further limited in this invention. For example, the projected outline of the upper electrode 4000 on the surface of the carrier 1000 can be an irregular shape or a regular shape, such as a triangle, rectangle, pentagon, hexagon, octagon, or other regular polygon.

[0047] Furthermore, it can be understood that... Figures 2a-2b The projection of the upper electrode 4000 onto the upper surface of the carrier 1000 falls within the range of the projection of the minimum cross-section of the cavity 1100 onto the upper surface of the carrier 1000, which is beneficial for the subsequent operation of the device.

[0048] A protective layer 5000 can also be formed on the upper electrode 4000. The material of the protective layer 5000 can be a silicon nitride layer or a silicon oxide layer.

[0049] When the thin-film bulk acoustic resonator is working, the electrical signal is applied between the upper electrode 4000 and the lower electrode 2000. The reverse piezoelectric effect causes the piezoelectric layer 3000 to mechanically expand or contract due to the polarization of the piezoelectric material. The cavity 1100 in the carrier 1000 needs to have a certain height reserved to prevent the sound waves generated by the vibration of the piezoelectric layer 3000 from propagating to the carrier 1000, thereby preventing sound wave leakage.

[0050] For the purposes of this disclosure, since the lower electrode 2000 falls entirely within the cavity 1100, the height of the cavity 1100 must be at least greater than or equal to the sum of the thickness of the lower electrode and the height required for the normal operation of the bulk acoustic wave resonator. For example, the height required for the normal operation of the bulk acoustic wave resonator is greater than or equal to 0.5 micrometers, and the thickness of the lower electrode is determined according to the parameters of the specific product, for example, it can be set between 0.1 and 0.5 micrometers. Furthermore, considering the operational stability of the bulk acoustic wave resonator, the height required for normal operation of the bulk acoustic wave resonator can be greater than or equal to 0.5 micrometers, and less than three-quarters of the thickness of the carrier 1000.

[0051] In the second specific embodiment provided in this disclosure, a seed crystal layer may be provided between the lower electrode 2000 and the cavity 1100. The seed crystal layer surrounds the side surface and the lower surface of the lower electrode 2000.

[0052] Furthermore, the seed layer is entirely located within the cavity 1100. Even further, there is at least a certain gap between the projected profile of the seed layer on the surface of the carrier 1000 and the projected profile of the minimum cross-section of the cavity 1100 on the surface of the carrier 1000; the gap is determined by a combination of the cavity angle and the thickness of the filling layer. More specifically, the gap between the projected profile of the seed layer on the surface of the carrier 1000 and the projected profile of the minimum cross-section of the cavity 1100 on the surface of the carrier 1000 is less than the sum of the height required for normal operation of the bulk acoustic resonator and the thickness of the seed layer. For example, the gap between the projected profile of the seed layer on the surface of the carrier 1000 and the projected profile of the minimum cross-section of the cavity 1100 on the surface of the carrier 1000 is 0.5-3 micrometers.

[0053] In the second specific implementation scheme, since the seed crystal layer is completely located within the cavity 1100, the height of the cavity 1100 needs to be at least greater than or equal to the sum of the thickness of the lower electrode 2000, the thickness of the seed crystal layer, and the height required for the normal operation of the bulk acoustic resonator.

[0054] In the third specific embodiment provided in this disclosure, a passivation layer is further provided between the seed crystal layer and the cavity 1100. The passivation layer surrounds the side surface and the lower surface of the seed crystal layer to protect the seed crystal layer and the lower electrode 2000 within the cavity 1100.

[0055] Furthermore, the passivation layer is entirely located within the cavity 1100. Even further, there is at least a certain gap between the projected profile of the passivation layer on the surface of the carrier 1000 and the projected profile of the minimum cross-section of the cavity 1100 on the surface of the carrier 1000. The gap is determined by a combination of the cavity angle and the thickness of the filling layer, and in a specific configuration, it can be less than the sum of the height required for normal operation of the bulk acoustic wave resonator, the thickness of the seed layer, and the thickness of the passivation layer. In the third specific embodiment, since the passivation layer is entirely located within the cavity 1100, the height of the cavity 1100 is at least greater than or equal to the sum of the thickness of the lower electrode 2000, the thickness of the seed layer, the thickness of the passivation layer, and the height required for normal operation of the bulk acoustic wave resonator.

[0056] In this disclosure, by forming the lower electrode 2000 within the cavity 1100 and ensuring that the lower surface of the piezoelectric layer 3000, the upper surface of the lower electrode 2000, and the upper surface of the carrier 1000 are on the same flat plane, the contact area between the piezoelectric layer 3000 and the lower electrode 2000 is free from abrupt inflection points. This improves the thin film crystal orientation of the piezoelectric layer 3000, avoids stress concentration problems at the contact portion between the piezoelectric layer 3000 and the lower electrode 2000, improves the reliability of the bulk acoustic wave resonator, reduces parasitic modes of the bulk acoustic wave resonator, avoids reducing the electromechanical coupling coefficient of the bulk acoustic wave resonator, and improves the product yield of the bulk acoustic wave resonator.

[0057] See Figures 3a-8b , Figures 3a-8a This is a schematic diagram illustrating the manufacturing process of a thin-film bulk acoustic resonator structure provided in a specific embodiment of this disclosure. Figure 3b-8b This is a schematic diagram of the manufacturing process of a thin-film bulk acoustic resonator structure provided in another specific embodiment of this disclosure.

[0058] More specifically, Figures 3a-8a A schematic diagram of the manufacturing process of a thin-film bulk acoustic resonator structure when the angle between each sidewall and the bottom of the cavity is 90°. Figure 3b-8b The angle formed between each sidewall and the bottom of the cavity is greater than 90° and less than or equal to 160°.

[0059] A schematic diagram of the manufacturing process of a thin-film bulk acoustic resonator structure.

[0060] like Figures 3a-3b As shown, a carrier 1000 is provided. For example, the carrier 1000 is a substrate. The selection of substrate material is as described above and will not be repeated here. The substrate mainly serves a supporting function.

[0061] A first photoresist is formed on a substrate, and the substrate is etched using the first photoresist as a mask to form a first etched portion 1110. Then, any remaining first photoresist is removed. The angles formed by the sidewalls of the first etched portion 1110 and the bottom surface of the first etched portion 1110 are set as follows: Figure 3a As shown, approximately 90 degrees, or as Figure 3b The angle shown is greater than 90 degrees and less than or equal to 160 degrees. The height of the first etched portion 1110 is set to be greater than or equal to the sum of the set over-polishing amount of the substrate, the range value of the chemical mechanical polishing flatness, the thickness of the lower electrode 2000, and the height required for the normal operation of the bulk acoustic wave resonator. The set over-polishing amount of the substrate is the amount of over-polishing of the substrate set after the lower electrode material layer is subsequently formed in order to completely remove the lower electrode material layer and filler layer material on the substrate surface other than the first etched portion 1110. The range value of the chemical mechanical polishing flatness is exemplarily 0-1000 angstroms. Preferably, the range value of the chemical mechanical polishing flatness is 0-600 angstroms.

[0062] It should also be understood that the carrier 1000 can also be a composite carrier comprising a substrate and a dielectric layer. Specifically, in its fabrication, a substrate is provided, a dielectric layer is formed on the substrate, a first photoresist is formed on the dielectric layer, the dielectric layer is etched using the first photoresist as a mask, and a first etched portion 1110 is formed in the dielectric layer or in both the dielectric layer and the substrate. Then, the remaining first photoresist is removed. The angle between each sidewall of the first etched portion 1110 and its bottom surface is set to be greater than or equal to 90 degrees and less than or equal to 160 degrees. The height of the first etched portion 1110 is greater than or equal to the sum of the set over-polishing amount of the dielectric layer, the range of chemical mechanical polishing flatness, the thickness of the lower electrode 2000, and the height required for the normal operation of the bulk acoustic wave resonator. The set over-polishing amount of the dielectric layer is the amount of over-polishing of the dielectric layer set after the subsequent formation of the fill layer and the lower electrode material layer to completely remove the lower electrode material and fill layer from the surface of the dielectric layer outside the first etched portion 1110.

[0063] Then, as Figures 4a-4bAs shown, a filler layer material 1200 and a lower electrode material layer are sequentially formed in the first etching section 1110. The filler layer material 1200 can be selected from thin film materials such as phosphosilicate glass, silicon dioxide, and amorphous silicon, which are compatible with the deposition temperature of subsequent thin films, do not contaminate the process system, and have good etching selectivity and chemical polishing properties with the lower electrode material. The specific selection of the lower electrode material is as described above and will not be repeated here. Those skilled in the art will understand that the thickness of the filler layer material is at least greater than or equal to the height required for the normal operation of the bulk acoustic wave resonator. This ensures that the distance between the lower surface of the lower electrode material layer formed in the first etching section 1110 and the bottom of the first etching section 1110 meets the height required for the normal operation of the bulk acoustic wave resonator.

[0064] Next, as Figures 5a-5b The planarization process shown is used on the carrier, such as chemical mechanical polishing. A polishing height is set to remove the lower electrode material and filler material from the carrier surface. To ensure thorough polishing, the carrier can be over-polished to partially remove the carrier material, forming the lower electrode 2000. The distance between the projected profile of the lower electrode 2000 on the surface of the carrier 1000 and the projected profile of the minimum cross-section of the cavity 1100 on the surface of the carrier 1000 is at least less than or equal to the thickness of the filler layer.

[0065] Furthermore, such as Figures 6a-6b As shown, after the formation of the filler layer 1200 and before the formation of the lower electrode 2000, a seed layer 1300 can be formed on the surface of the substrate using techniques such as atomic layer deposition to promote the growth of the lower electrode material layer. Next, the carrier 1000 is subjected to a planarization process, such as chemical mechanical polishing, setting a polishing height to remove the bottom electrode material, seed layer 1300, and filler layer material 1200 from the surface of the carrier 1000. To ensure thorough polishing, the carrier can be over-polished to partially remove the carrier material.

[0066] Furthermore, such as Figures 7a-7b As shown, after forming the filler layer material 1200 and before forming the seed layer 1300, a passivation layer 1400 can be formed on the surface of the substrate using thin film deposition technology to avoid damage to the seed layer 1300 when the filler layer is removed to release the cavity. Next, the carrier 1000 is subjected to a planarization process, such as chemical mechanical polishing, with a set polishing height to remove the bottom electrode material, seed layer, passivation layer, and filler material from the surface of the carrier 1000. To ensure thorough polishing, the carrier 1000 can be over-polished to partially remove the carrier material.

[0067] Understandably, a passivation layer can be formed on the surface of the substrate using thin film deposition technology after the formation of the filler layer 1200 and before the formation of the lower electrode 2000, to avoid damage to the lower electrode 2000 when removing the filler layer to release the cavity. Next, a planarization process is performed on the carrier 100, such as chemical mechanical polishing, setting the polishing height to remove the bottom electrode material, passivation layer, and filler material from the carrier surface. To ensure thorough polishing, the carrier can be over-polished to partially remove the carrier material.

[0068] Then, as Figures 8a-8b As shown, a piezoelectric layer 3000 is deposited on the carrier 1000. The material of the piezoelectric layer 3000 can be selected to meet the bandwidth requirements of wireless mobile communication signal transmission and reception. As mentioned before, materials compatible with semiconductor processes, such as aluminum nitride (AlN) or zirconate titanate (PZT), are preferred.

[0069] Next, an upper electrode material layer is deposited on the piezoelectric layer 3000, and the upper electrode 4000 is etched to form it. Other structures of the thin-film bulk acoustic resonator, such as the protective layer 5000, are then fabricated. When the cavity is filled with sacrificial material as a filling layer, the sacrificial material is further removed, releasing the cavity 1100. This results in the final formation of... Figures 8a-8b The structure of the bulk acoustic resonator shown is illustrated.

[0070] The manufacturing process of the thin-film bulk acoustic wave resonator structure disclosed herein utilizes planarization processes such as chemical mechanical polishing to form the bottom electrode. This avoids abrupt inflection points at the contact area between the bottom electrode and the piezoelectric layer, overcoming the stress problem caused by abrupt inflection points at the contact area between the bottom electrode and the piezoelectric layer in the prior art, and improving the thin-film crystal orientation of the piezoelectric layer. Furthermore, the manufacturing process of the thin-film bulk acoustic wave resonator structure disclosed herein does not require the formation of small tilted structures at the edge region of the bottom electrode, saving the steps of photolithography, etching, and resist removal cleaning of the bottom electrode, thus simplifying the process.

[0071] Furthermore, the thin-film bulk acoustic resonator provided in this disclosure can be used to form a filter, which can be used in portable communication devices such as mobile phones, personal digital assistants (PDAs), personal wearable devices, and video game devices. The filter can include any of the thin-film acoustic resonators disclosed in this disclosure.

[0072] Furthermore, the bulk acoustic resonator structure and fabrication method disclosed herein can be applied to various electronic devices.

[0073] The present disclosure has been described above with reference to specific implementation schemes. However, those skilled in the art should understand that these descriptions are exemplary and not intended to limit the scope of protection of the present disclosure. Those skilled in the art can make various modifications and variations to the present disclosure based on its spirit and principles, and such modifications and variations are also within the scope of the present disclosure.

Claims

1. A method for manufacturing a bulk acoustic resonator, characterized in that, include: Provide a carrier; A first etched portion is formed by etching in the carrier; In the first etched section, a filler material and a lower electrode material layer are sequentially deposited conformally, wherein the thickness of the filler material is greater than or equal to the height required for the bulk acoustic resonator to operate normally. The lower electrode material layer and the filler material on the upper surface of the carrier are removed by a planarization process, and a filler layer and a lower electrode are formed in the first etched portion. The upper surface of the lower electrode, the upper surface of the filler layer and the upper surface of the carrier are on the same plane. A piezoelectric layer is formed on the carrier, wherein the lower surface of the piezoelectric layer, the upper surface of the carrier, the upper surface of the filler layer, and the upper surface of the lower electrode are in the same plane; The height of the first etched portion is at least greater than the sum of the over-grinding amount of the carrier, the flatness range of the planarization process, the thickness of the lower electrode, and the height required for the normal operation of the bulk acoustic resonator, as set in the planarization process.

2. The manufacturing method as described in claim 1, characterized in that: Before forming the lower electrode, a seed layer is formed in the first etched section.

3. The manufacturing method as described in claim 2, characterized in that: The height of the first etched portion is at least greater than the sum of the over-grinding amount of the carrier, the flatness range of the planarization process, the thickness of the seed layer, the thickness of the lower electrode, and the height required for the normal operation of the bulk acoustic resonator.

4. The manufacturing method as described in claim 1, characterized in that: Before forming the seed layer, a passivation layer is formed in the first etched section.

5. The manufacturing method as described in claim 2, characterized in that: The height of the first etched portion is at least greater than the sum of the over-grinding amount of the carrier, the flatness range of the planarization process, the thickness of the passivation layer, the thickness of the seed layer, the thickness of the lower electrode, and the height required for the normal operation of the bulk acoustic resonator.

6. The manufacturing method as described in claim 1, 3, or 5, characterized in that: The angle between each sidewall of the first etched portion and the bottom surface of the first etched portion is 90-160°.

7. The manufacturing method as described in claim 6, characterized in that: The carrier is a single substrate or a composite structure consisting of a substrate and a dielectric layer.

8. The manufacturing method as described in claim 6 or 7, characterized in that: The interval between the projection profile of the lower electrode on the carrier and the projection profile of the minimum cross-section of the first etched portion on the carrier is less than or equal to the thickness of the filling material.

9. The manufacturing method as described in claim 8, characterized in that: An upper electrode is formed on the piezoelectric layer; the projection profile of the upper electrode on the carrier falls within the projection profile of the smallest cross section of the first etched portion on the carrier; after the upper electrode is formed, the filler layer in the first etched portion is removed.

10. A bulk acoustic resonator, characterized in that, include: A carrier in which a cavity is formed; A lower electrode is formed within the cavity, and the upper surface of the lower electrode is in the same plane as the upper surface of the carrier. A piezoelectric layer is formed on the carrier, wherein the lower surface of the piezoelectric layer, the upper surface of the carrier, and the upper surface of the lower electrode are in the same plane; The height of the cavity is at least greater than or equal to the thickness of the lower electrode and the sum of the height required for the normal operation of the bulk acoustic resonator. The interval between the projection profile of the lower electrode on the carrier and the projection profile of the minimum cross-section of the cavity on the carrier is less than or equal to the height required for the bulk acoustic resonator to operate normally.

11. The bulk acoustic resonator as described in claim 10, characterized in that: The height required for the bulk acoustic resonator to operate normally is greater than or equal to 0.5 μm; the thickness of the lower electrode is between 0.1 and 0.5 μm.

12. The bulk acoustic resonator as described in claim 11, characterized in that: It also has a seed crystal layer located within the cavity, surrounding the side and lower surfaces of the lower electrode. The interval between the projected profile of the seed crystal layer on the carrier and the projected profile of the minimum cross-section of the cavity on the carrier is less than or equal to the sum of the height required for the normal operation of the bulk acoustic resonator and the thickness of the seed crystal layer.

13. The bulk acoustic resonator as described in claim 12, characterized in that: The height of the cavity is at least greater than or equal to the sum of the thickness of the lower electrode, the thickness of the seed layer, and the height required for the normal operation of the bulk acoustic resonator.

14. The bulk acoustic resonator as described in claim 13, characterized in that: It also has a passivation layer located inside the cavity, surrounding the side and bottom surfaces of the seed crystal layer. The distance between the projection profile of the passivation layer on the carrier and the projection profile of the minimum cross-sectional area of ​​the cavity on the carrier is less than or equal to the sum of the height required for normal operation of the bulk acoustic resonator, the thickness of the seed crystal layer, and the thickness of the passivation layer.

15. The bulk acoustic resonator as described in claim 14, characterized in that: The height of the cavity is at least greater than or equal to the thickness of the lower electrode, the thickness of the seed layer, the thickness of the passivation layer, and the sum of the thickness required for the normal operation of the bulk acoustic resonator.

16. The bulk acoustic resonator as described in claim 11, 13, or 15, characterized in that: The angle between each sidewall of the cavity and the bottom surface of the cavity is 90-160°.

17. The bulk acoustic resonator as described in claim 15 or 16, characterized in that: The carrier is a single substrate or a composite structure consisting of a substrate and a dielectric layer.

18. An electronic device, characterized in that: Includes a bulk acoustic resonator as described in any one of claims 1-17.

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