Filter and method for forming the same, electronic device

Abstract

A filter and a forming method thereof and an electronic device, the forming method comprising: after providing a piezoelectric laminated structure, a first thinning treatment is performed on a passivation layer in a target resonant region, so that the thickness of the passivation layer in the target resonant region is less than that in other resonant regions, and the vibration frequency of the passivation layer in the target resonant region is faster than that in other resonant regions, the frequency of the resonator in the target resonant region is right-shifted, which is beneficial to making the target resonant region used to form the resonator with the highest vibration frequency, and the performance of the filter bandwidth corresponding to the filter bandwidth is increased, because the first thinning treatment further reduces the surface roughness of the passivation layer in the target resonant region, which means that the thickness uniformity of the passivation layer in the target resonant region is improved, so that the right side frequency of the filter bandwidth is modulated, and the uniformity of the right side frequency of the filter bandwidth is improved, and more frequency points will fall within the range required by the specification during measurement, which is beneficial to improve the yield of the filter.

Description

Technical Field

[0001] This invention relates to the field of semiconductors, and more particularly to a filter, a method for forming the filter, and an electronic device thereof. Background Technology

[0002] Since the development of analog radio frequency (RF) communication technology in the early 1990s, RF front-end modules have gradually become core components of communication equipment. Among all RF front-end modules, filters have become the fastest-growing and most promising component. With the rapid development of wireless communication technology and the increasing maturity of 5G communication protocols, the market has also set more stringent standards for the performance of RF filters. The performance of a filter is determined by the resonator units that make up the filter. Among existing filters, thin-film bulk acoustic resonators (FBARs) have become one of the most suitable filters for 5G applications due to their small size, low insertion loss, high out-of-band rejection, high quality factor, high operating frequency, large power capacity, and good ESD resistance.

[0003] Typically, a thin-film bulk acoustic resonator includes two thin-film electrodes with a piezoelectric thin-film layer between them. The thin-film electrodes and piezoelectric thin-film layer form a piezoelectric stack structure. Its working principle involves the piezoelectric thin-film layer vibrating under an alternating electric field. This vibration excites a bulk acoustic wave propagating along the thickness of the piezoelectric thin-film layer. This acoustic wave is reflected back at the interface between the upper and lower electrodes and the air, and then reflects back and forth within the thin film, forming oscillations. When the acoustic wave propagates within the piezoelectric thin-film layer for an odd multiple of half its wavelength, a standing wave oscillation is formed.

[0004] In the thin-film bulk acoustic resonator, a signal electrode is formed on one side of the piezoelectric stack structure, penetrating one thin-film electrode and the piezoelectric thin-film layer and electrically connected to another thin-film electrode. The signal electrode is used as the input and output of the piezoelectric stack structure signal.

[0005] However, thin-film bulk acoustic resonators cannot meet the requirements of high-performance radio frequency systems. Summary of the Invention

[0006] The problem solved by this invention is to provide a filter and its formation method, as well as an electronic device, to improve the performance of the filter.

[0007] To address the aforementioned problems, the present invention provides a method for forming a filter, comprising: providing a piezoelectric stack structure, the piezoelectric stack structure including a piezoelectric layer, the piezoelectric layer including a first side and a second side opposite to the first side, the piezoelectric stack structure further including a first electrode located on the first side and a second electrode located on the second side; the piezoelectric stack structure including a plurality of resonant regions distributed on a plane, the resonant regions being used to form resonators, the plurality of resonant regions including a target resonant region for forming a resonator with the highest vibration frequency; forming a passivation material layer covering the first electrode on the first side; and performing a first thinning process on the passivation material layer of the target resonant region to form a passivation layer.

[0008] Accordingly, the present invention also provides a filter, comprising: a piezoelectric stack structure, the piezoelectric stack structure including a piezoelectric layer including a first side and a second side opposite to the first side, the piezoelectric stack structure further including a first electrode located on the first side and a second electrode located on the second side; the piezoelectric stack structure including a plurality of resonant regions distributed in a plane, the resonant regions being used to form resonators, the plurality of resonant regions including a target resonant region for forming a resonator with the highest vibration frequency; and a passivation layer located on the first electrode, the passivation layer thickness in the target resonant region being less than the passivation layer thickness in the other resonant regions.

[0009] Accordingly, the present invention also provides an electronic device including the aforementioned filter.

[0010] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0011] In a filter formation method provided by an embodiment of the present invention, a piezoelectric stack structure is provided. The piezoelectric stack structure includes a piezoelectric layer, including a first side and a second side opposite to the first side. The piezoelectric stack structure also includes a first electrode located on the first side and a second electrode located on the second side. The piezoelectric stack structure includes a plurality of resonant regions, which are used to form resonators. Among the plurality of resonant regions, a target resonant region is included for forming a resonator with the highest vibration frequency. After providing the piezoelectric stacked structure, a passivation material layer is formed on the first electrode on the second side. The first thinning process thins the passivation material layer in the target resonant region, so that the passivation layer thickness in the target resonant region is less than that in other resonant regions. Because the thinner the passivation layer, the higher the vibration frequency, the passivation layer vibration frequency in the target resonant region is faster than that in other resonant regions. The frequency of the resonator in the target resonant region shifts to the right (i.e., the high frequency value increases), which is beneficial for the target resonant region to form the resonator with the highest vibration frequency. The corresponding filter bandwidth is increased because the first thinning process further reduces the surface roughness of the passivation layer in the target resonant region, which means that the uniformity of the passivation layer thickness formed in the target resonant region is improved. This modulates the frequency (high frequency value) on the right side of the filter bandwidth, improving the uniformity of the frequency on the right side of the filter bandwidth. During measurement, more frequency points will fall within the specified range, which is beneficial for improving the yield of the filter.

[0012] An embodiment of the present invention provides a filter comprising a piezoelectric stack structure, the piezoelectric stack structure comprising a piezoelectric layer, including a first side and a second side opposite to the first side, the piezoelectric stack structure further comprising a first electrode located on the first side and a second electrode located on the second side; the piezoelectric stack structure includes a plurality of resonant regions, the resonant regions being used to form resonators, and the plurality of resonant regions including a target resonant region for forming a resonator with the highest vibration frequency. The passivation layer thickness in the target resonant region is less than that in other resonant regions. Because a thinner passivation layer results in a higher vibration frequency, the passivation layer vibration frequency in the target resonant region is faster than that in other resonant regions. The frequency of the resonator in the target resonant region shifts to the right (i.e., the high-frequency value increases), which is beneficial for the target resonant region to form the resonator with the highest vibration frequency. The corresponding filter bandwidth is increased because the first thinning process further reduces the surface roughness of the passivation layer in the target resonant region, which means that the uniformity of the passivation layer thickness in the target resonant region is improved. This modulates the frequency (high-frequency value) on the right side of the filter bandwidth, improving the uniformity of the frequency on the right side of the filter bandwidth. During measurement, more frequency points will fall within the specified range, which is beneficial for improving the filter yield. Attached Figure Description

[0013] Figures 1 to 4This is a schematic diagram of the structure corresponding to each step in a method for forming a resonator;

[0014] Figures 5 to 16 This is a schematic diagram of the structure corresponding to each step in the filter formation method of the present invention. Detailed Implementation

[0015] As the background technology shows, film bulk acoustic resonators (FBARs) are currently widely used. This paper analyzes the reasons for poor device performance in conjunction with a filter fabrication method.

[0016] A method for forming a filter includes: such as Figure 1 As shown, a piezoelectric stack structure is provided, the piezoelectric stack structure including a plurality of resonant regions distributed in a plane. Figure 1 (Only one resonant region is shown in the image). The resonant region includes a working region I and a peripheral region II surrounding the working region I. The piezoelectric stack structure includes a piezoelectric layer 1, a first electrode 2 located on a first side of the piezoelectric layer 1, and a second electrode 4 located on a second side of the piezoelectric layer 1. The first side and the second side are two opposite sides of the piezoelectric layer 1.

[0017] like Figure 2 As shown, a mass-loaded material layer (not shown) is formed on the first electrode 2 from the first side; a photoresist layer 7 is formed on the mass-loaded material layer; using the photoresist layer 7 as a mask, the mass-loaded material layer in the working area I is thinned to form a mass-loaded layer 3. An etching machine is typically used to thin the mass-loaded material layer.

[0018] like Figure 3 As shown, a passivation material layer 5 is formed on the second electrode 4.

[0019] like Figure 4 As shown, the passivation material layer 5 is thinned to form the passivation layer 6.

[0020] The existing filter frequency tuning process involves thinning the mass load material layer of multiple resonant regions to different thicknesses, resulting in varying thicknesses of the mass load layer 3 in the working region I of each resonant region, thereby obtaining a specific bandwidth for the filter. Frequency adjustment is then achieved by similarly thinning the passivation material layer 5 in multiple resonant regions, ensuring the filter bandwidth reaches the target frequency range and improving the uniformity of the frequency (low frequency values) on the left side of the filter bandwidth. However, it has been found that during the thinning process of the mass load material layer in the working region I, abnormal conditions such as etching equipment fluctuations can cause differences between the thinned thickness and the expected thinning thickness in each working region I. This results in fluctuations in the frequency (high frequency values) on the right side of the filter bandwidth, and the frequency uniformity on the right side does not meet requirements, leading to a low filter yield.

[0021] The filter formation method provided in this embodiment of the invention provides a piezoelectric stack structure, which includes a piezoelectric layer, a first side and a second side opposite to the first side, a first electrode located on the first side and a second electrode located on the second side; the piezoelectric stack structure includes a plurality of resonant regions, which are used to form a resonator, and the plurality of resonant regions include a target resonant region for forming a resonator with the highest vibration frequency. After providing the piezoelectric stacked structure, a passivation material layer is formed on the first electrode on the second side. The first thinning process thins the passivation material layer in the target resonant region, so that the passivation layer thickness in the target resonant region is less than that in other resonant regions. Because the thinner the passivation layer, the higher the vibration frequency, the passivation layer vibration frequency in the target resonant region is faster than that in other resonant regions. The frequency of the resonator in the target resonant region shifts to the right (i.e., the high frequency value increases), which is beneficial for the target resonant region to form the resonator with the highest vibration frequency. The corresponding filter bandwidth is increased because the first thinning process further reduces the surface roughness of the passivation layer in the target resonant region, which means that the uniformity of the passivation layer thickness formed in the target resonant region is improved. This modulates the frequency (high frequency value) on the right side of the filter bandwidth, improving the uniformity of the frequency on the right side of the filter bandwidth. During measurement, more frequency points will fall within the specified range, which is beneficial for improving the yield of the filter.

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0023] Figures 5 to 16 This is a schematic diagram of the structure corresponding to each step in the filter formation method of the present invention.

[0024] refer to Figure 5A piezoelectric stack structure 102 is provided, the piezoelectric stack structure 102 including a plurality of resonant regions distributed in a plane, the resonant regions being used to form resonators, and the plurality of resonant regions including a target resonant region for forming a resonator with the highest vibration frequency. Figure 5 (Only the target resonant region is shown in the diagram).

[0025] Different resonant regions are used to form resonators with corresponding resonant frequencies. The resonators are used to select a specific frequency, generate a stable oscillation signal, and provide frequency control and amplification functions.

[0026] In this embodiment, the filter to be formed includes three resonators, and the corresponding piezoelectric stack structure 102 includes three resonant regions, which are low resonant region, medium resonant region and high resonant region according to the vibration frequency of the resonators used to form. The target resonant region is the high resonator.

[0027] It should be noted that the resonant region includes the operating region I and the peripheral region II surrounding the operating region I. The operating region I of the resonator refers to the area capable of storing and releasing energy. It is composed of energy storage elements (such as capacitors and inductors). The main function of the operating region I is to maintain oscillation, that is, to store and transfer energy, enabling the resonator to maintain stable amplitude and frequency. The peripheral region II of the resonator refers to other circuits or components connected to the resonator. The function of the peripheral region II is to provide a path for exchanging energy with the resonator.

[0028] In this embodiment, the piezoelectric stack structure 102 includes a piezoelectric layer 105, the piezoelectric layer 105 includes a first side 1051 and a second side 1052 opposite to the first side 1051, the piezoelectric stack structure 102 also includes a first electrode 104 located on the first side 1051 of the piezoelectric layer 105 and a second electrode 106 located on the second side 1052 of the piezoelectric layer 105.

[0029] The piezoelectric stack structure 102 prepares for the subsequent formation of a resonator. The corresponding piezoelectric stack structure 102 is used to realize the mutual conversion between electrical signals and acoustic signals, so that the filter can filter the signals.

[0030] In this embodiment, the first electrode 104 serves as the upper electrode of the piezoelectric stack structure 102.

[0031] The material of the first electrode 104 is a conductive material. The conductive material can be a metallic material with conductive properties, such as one or more of the following: Mo, Al, Cu, Pt, Au, Ir, Os, Re, Pd, Rh, Ru, Mo, and W.

[0032] The piezoelectric layer 105 is made of a piezoelectric material, a crystalline material that exhibits a voltage between its two ends when subjected to pressure. Piezoelectric materials possess the piezoelectric effect, which allows for the conversion between mechanical vibration (sound waves) and alternating current, thereby achieving the conversion of sound energy into electrical energy. The piezoelectric layer 105 can be made of piezoelectric materials with a wurtzite-type crystalline structure, such as ZnO, AlN, GaN, aluminum zirconate titanate, or lead titanate. In this embodiment, the piezoelectric layer 105 is made of AlN. In this embodiment, chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD) processes can be used to form the piezoelectric layer 105.

[0033] In this embodiment, the second electrode 106 serves as the upper electrode of the piezoelectric stack structure 102.

[0034] The material of the second electrode 106 is a conductive material. The conductive material can be a metallic material with conductive properties, such as one or more of the following: Mo, Al, Cu, Pt, Au, Ir, Os, Re, Pd, Rh, Ru, Mo, and W.

[0035] It should be noted that in the step of providing the piezoelectric stack structure 102, the piezoelectric stack structure 102 is formed on the temporary substrate 100.

[0036] In this embodiment, the temporary substrate 100 can be any suitable semiconductor substrate, such as a bulk silicon substrate, and it can also be at least one of the following materials: SiGe, SiC, SiGeC, TnAs, GaAs, Inp, or other group III and group V compound semiconductors.

[0037] It should also be noted that the method of forming the filter further includes: after providing the temporary substrate 100 and before providing the first electrode 104, forming a first buffer layer (not shown in the figure) on the temporary substrate 100.

[0038] The first buffer layer is used to improve the interface quality of the temporary substrate 100 surface and to act as a buffer between the first electrode 104 and the temporary substrate 100, thereby improving the growth consistency of the first electrode 104 and the adhesion between the temporary substrate 100 and the first electrode 104. During the subsequent removal of the temporary substrate 100, the first buffer layer also serves as a stop layer, which helps prevent the subsequent removal process from affecting the first electrode 104.

[0039] In this embodiment, the material of the first buffer layer can be one or more of silicon oxide, silicon nitride, and silicon oxynitride. The first buffer layer is formed using a deposition process, such as chemical vapor deposition or atomic layer deposition.

[0040] refer to Figure 6 and Figure 7 The method of forming the filter further includes forming a mass load layer 101 on the second electrode 106 from the second side 1052.

[0041] The mass load layer 101 is used to effectively reflect the transverse modes into the working region I, effectively suppressing the transverse leakage of energy, thereby improving the Q value.

[0042] In this embodiment, the mass load layer 101 is either a continuous ring or a non-continuous ring.

[0043] It should be noted that the 1nm thick mass loading layer 101 corresponds to a frequency response of 1.8MHz to 2.2MHz. In this embodiment, the material of the mass loading layer 101 is Mo. In other embodiments, the material of the mass loading layer may also include W or Au.

[0044] It should be noted that the thickness of the mass load layer 101 in the working region I varies in each of the resonant regions. Specifically, the mass load layer 101 in the high resonance region is the thinnest, followed by the mass load layer 101 in the medium resonance region, and the mass load layer 101 in the low resonance region is the thickest. Correspondingly, the mass load layer 101 in the target resonance region has the smallest thickness. The vibration frequencies of the mass load layer 101 with different thicknesses are different. Specifically, the thicker the mass load layer 101, the lower the resonant frequency of the resonator; the thinner the mass load layer 101, the higher the resonant frequency of the resonator. The resonators formed in the high, medium, and low resonance regions have different resonant frequency ranges, enabling the selection of a specific frequency. These resonators with different vibration frequencies constitute the frequency response range of the filter, i.e., its bandwidth.

[0045] Specifically, the step of forming a mass loading layer 101 on the second electrode 106 from the second side 1052 includes: forming a mass loading material layer 123 (e.g., ...) on the second electrode 106 from the second side 1052. Figure 6 (as shown); a mass load mask layer 107 (e.g., as shown) is formed on the mass load material layer 123. Figure 6 (As shown); using the mass load mask layer 107 as a mask, the mass load material layer 123 is etched to form the mass load layer 101.

[0046] In this embodiment, the material of the first mask layer 107 includes photoresist.

[0047] It should be noted that in the step of etching the mass load material layer 123, the mass load material layer 123 in the working area I of each of the resonant regions is thinned to a different thickness, so that the remaining thickness of the mass load material layer 123 in different resonant regions is different, thus forming the mass load layer 101.

[0048] In this embodiment, there are three resonant regions. During the process of thinning the mass load layer 101 of different resonant regions to different thicknesses, the mass load mask layer 107 used includes a first mask layer, a second mask layer, and a third mask layer. Specifically, a first mask layer is formed that covers the intermediate and high resonant regions and exposes the low resonant region. The mass load material layer 123 of the low resonant region is thinned through the first mask layer. A second mask layer (not shown in the figure) is formed that covers the intermediate and low resonant regions and exposes the high resonant region. The mass load material layer 123 of the high resonant region is thinned through the second mask layer. A third mask layer is formed that covers the low and high resonant regions and exposes the intermediate resonant region. The mass load material layer 123 of the intermediate resonant region is thinned through the third mask layer.

[0049] It should be noted that the thinning process of the mass load material layer 123 in each resonant region is performed specifically on the mass load material layer 123 of the working region I of each resonant region. In other embodiments, the mass load material layers of both the working region and the peripheral region can be thinned simultaneously.

[0050] As an example, the mass load material layer 123 in the high resonance region has a thinning thickness of 600 to 700 Å, the mass load material layer 123 in the medium resonance region has a thinning thickness of 500 to 600 Å, and the mass load material layer 123 in the low resonance region has a thinning thickness of 300 to 400 Å.

[0051] In this embodiment, a chemical vapor deposition (CVD) or physical vapor deposition (PVD) process is used to form the mass-loaded material layer 123. In other embodiments, an atomic layer deposition (ALD) process can also be used to form the mass-loaded material layer in order to improve the density of the mass-loaded layer.

[0052] In this embodiment, the mass-loaded material layer 123 is thinned using an ion beam etching (IBE) process.

[0053] It should be noted that an etching apparatus is used to perform ion beam etching on the mass load material layer 123. As the size of the filter becomes smaller and smaller, the thickness of the mass load layer 101 in the filter also becomes smaller and smaller, and the fluctuation error of the etching apparatus has an increasingly greater impact on the thickness of the mass load layer 101.

[0054] Therefore, to address the impact of etching equipment fluctuation errors on the thickness of the mass load layer 101, the filter formation method further includes: providing an expected thickness of the mass load layer 101 in the working region I of the target resonant region; in the step of forming the mass load layer 101 on the second electrode 106 from the second side 1052, the thickness of the mass load layer 101 in the working region I of the target resonant region is greater than the expected thickness.

[0055] It should be noted that the filter formation method further includes: after providing the piezoelectric stack structure 102, forming a passivation material layer covering the first electrode 104 on the first side 1051, and performing a first thinning process on the passivation material layer in the target resonant region to form a passivation layer. The thickness of the mass load layer 101 in the working region I of the target resonant region is greater than the expected thickness, so that the subsequent first thinning process on the passivation material layer has a thinning margin.

[0056] In this embodiment, the difference between the thickness of the mass load layer 101 in the working area I of the target resonant region and the expected thickness is greater than the fluctuation error of the etching machine. Even if too much mass load material layer 123 is etched due to the etching fluctuation error of the machine, the thickness of the mass load layer 101 in the working area I of the target resonant region is greater than the expected thickness.

[0057] It should be noted that the difference between the thickness of the mass load layer 101 in the working region I of the target resonant region and the expected thickness should not be too large or too small. If the difference is too large, the thickness to be reduced in the subsequent first thinning process of the passivation material layer will be too large, requiring excessive processing time and increasing costs. If the difference is too small, i.e., the thinning margin provided for the subsequent first thinning process of the passivation material layer is too small, it places stringent requirements on the control capability of the passivation material layer etching process; otherwise, the thickness of the formed passivation layer may be too thin, causing the detection frequency band of the filter to fail to meet the design requirements. In this embodiment, the difference between the thickness of the mass load layer 101 in the working region I of the target resonant region and the expected thickness is 20 angstroms to 40 angstroms.

[0058] It should be noted that after the mass load layer 101 is formed, the thickness of the mass load layer 101 in each working area I is also measured to pre-design the thickness value for the subsequent second thinning process of the passivation material film, so that the thickness of the formed passivation material layer is within an appropriate range, and the left frequency of the filter (i.e. the lowest frequency value of the filter bandwidth) meets the design requirements.

[0059] In this embodiment, a scanning electron microscope (SEM) is used to measure the thickness of the mass load layer 101 in each working area I.

[0060] refer to Figure 8 The filter formation method further includes: after forming the mass load layer 101, etching the second electrode 106 in the edge portion of the working area I to form a bottom air trench (BAT) 125 exposing the piezoelectric layer 105.

[0061] The step of forming the bottom air groove 125 includes: forming a shielding layer (not shown in the figure) on the second electrode 106, the shielding layer exposing the area where the bottom air groove is to be formed; etching the second electrode 106 with the shielding layer as a mask to form the bottom air groove 125 exposing the piezoelectric layer 105.

[0062] The bottom air slot 125 is used to reflect sound waves laterally, which helps to increase the residence time of sound waves in the cavity, thereby reducing energy dissipation and improving the acoustic-electric conversion performance of the resonator.

[0063] In this embodiment, the shielding layer includes an organic material layer. Accordingly, the shielding layer is formed using a spin coating process.

[0064] In this embodiment, the second electrode 106 is etched using a dry etching process with a masking layer as a shield to form a bottom air groove 125 that penetrates the second electrode 106 and exposes the piezoelectric layer 105. The dry etching process is an anisotropic etching process, which gives the bottom air groove 125 better control over the etching profile, making it easier to ensure that the morphology of the bottom air groove 125 meets the process requirements.

[0065] The method for forming the resonator also includes: after forming the bottom air groove 125, removing the shielding layer.

[0066] It should be noted that in the step of forming the bottom air groove 125, the shielding layer also exposes part of the edge area of ​​the peripheral region II; in the step of etching the second electrode 106 with the shielding layer as a mask, the edge area of ​​the peripheral region II of the second electrode 106 is also etched with the shielding layer as a mask, in order to separate the second electrodes 106 of different resonant regions.

[0067] Continue to refer to Figure 8 The method of forming the resonator further includes: after forming the bottom air groove 125, forming a first support layer 111 from the side of the second electrode 106 that covers the peripheral area II and exposes the working area I.

[0068] The first support layer 111 prepares for subsequent bonding of the first substrate.

[0069] In this embodiment, the first support layer 111 has a first opening 110, which exposes the second electrode 106 of the working area I.

[0070] In this embodiment, the first support layer 111 sequentially includes a filling layer (not shown in the figure), an etch stop layer (not shown in the figure), and a second buffer layer (not shown in the figure) in the direction away from the piezoelectric stack structure 102.

[0071] In this embodiment, the shape of the bottom surface of the first opening 110 can be a rectangle or a polygon other than a rectangle, such as a pentagon, hexagon, or octagon, or it can be a circle or an ellipse. In other embodiments, the longitudinal cross-sectional shape of the second opening can also be a spherical cap that is wider at the top and narrower at the bottom, that is, its longitudinal cross-section is U-shaped.

[0072] It should be noted that the method of forming the resonator also includes: after forming the bottom air groove 125, forming a protective layer (not shown in the figure) on the end face of the first support layer 111 away from the piezoelectric stack structure 102, the side wall of the first support layer 111, and the second electrode 106 exposed by the first support layer 111.

[0073] The protective layer prepares for subsequent bonding of the first substrate to the end face of the first support layer 111 facing away from the piezoelectric stack structure 102. The protective layer also serves to isolate the second electrode 106 exposed by the first opening 110 from external moisture, making the surface of the second electrode 106 less prone to oxidation. This improves the reliability of the resonator performance, enabling the resonator to meet the requirements of high-performance radio frequency systems. Furthermore, because of the protective layer, as the operating temperature increases during resonator operation, the vibration frequency of the protective layer increases, which can, to some extent, compensate for the decrease in the vibration frequency of the piezoelectric layer 105. This helps prevent the vibration frequency of the piezoelectric stack structure 102 and the protective layer as a whole from decreasing excessively, thus improving the temperature drift coefficient of the piezoelectric resonator and enhancing its reliability.

[0074] The protective layer is made of one or more of tetraethyl orthosilicate (TEOS), silicon oxide, and silicon nitride. In this embodiment, the protective layer is formed using a chemical vapor deposition process.

[0075] It should be noted that the forming method further includes: forming an edge protrusion structure 131 (Frame) around the effective resonant region in the working area I on the second electrode 106, which is used to change the acoustic impedance of the edge, prevent energy leakage from the working area I, and improve the quality factor of the resonator.

[0076] In this embodiment, the material of the edge protrusion structure 131 is different from the material of the second electrode 106. In other embodiments, the material of the edge protrusion structure can also be the same as the material of the second electrode. When the edge protrusion structure and the second electrode are made of the same material, the edge protrusion structure and the second electrode can be formed by etching the same material, and the corresponding edge protrusion structure and the second electrode are an integral structure.

[0077] refer to Figure 9 The method for forming the filter further includes: before forming the passivation material layer, forming a first cavity 115 on the side of the second electrode 106 away from the piezoelectric layer 105.

[0078] The first cavity 115 helps reduce the vibration energy loss of the resonator and can improve the acoustic-electric conversion performance of the resonator.

[0079] Specifically, the steps for forming the first cavity 115 include: providing a first substrate 112; bonding the first substrate 112 onto a first support layer 111, wherein the first substrate 112, the second electrode 106, and the first support layer 111 form the first cavity 115.

[0080] The first substrate 112 can be any suitable substrate known to those skilled in the art, such as at least one of the following materials: silicon, germanium, germanium silicon, silicon carbon, silicon carbon germanium silicon, indium arsenide, gallium arsenide, indium phosphide, or other group III / V compound semiconductors.

[0081] It should be noted that the first substrate 112 is bonded to the protective layer on the first support layer 111, and the contact surface between the protective layer and the first substrate 112 is bonded by Si-O-Si covalent bonds.

[0082] refer to Figure 10 The method for forming the filter further includes: after forming the first cavity 115, removing the temporary substrate 100 and the first buffer layer. In this embodiment, the temporary substrate 100 can be removed by a thinning process or a stripping process.

[0083] In this embodiment, a combination of dry and wet methods is used to remove the first buffer layer.

[0084] refer to Figure 11 and Figure 12 A passivation material layer 124 covering the first electrode 104 is formed on the first side 1051 (e.g., ...). Figure 12 (As shown).

[0085] The passivation material layer 124 is prepared for the subsequent first thinning process to form a passivation layer.

[0086] The materials of the passivation material layer 124 and the mass load layer 101 have different frequency change rates, i.e., different frequency response characteristics. In this embodiment, the ratio of the frequency change rate of the mass load layer and the passivation layer is 4 to 6.66.

[0087] In this embodiment, the frequency response of the 1nm thick passivation material layer 124 is 0.3MHz to 0.5MHz. Specifically, the material of the passivation material layer 124 is silicon nitride.

[0088] The step of forming a passivation material layer 124 covering the first electrode 104 on the first side 1051 includes: as follows Figure 11 As shown, a passivation material film 103 covering the first electrode 104 is formed on the first side 1051; as Figure 12 As shown, the passivation material film 103 undergoes a second thinning process 109 to form the passivation material layer 124.

[0089] In this embodiment, in the step of forming a passivation material film 103 covering the first electrode 104 on the first side 1051, the thickness of the passivation material film 103 is 300 angstroms to 1000 angstroms.

[0090] In this embodiment, a passivation material film 103 is formed using chemical vapor deposition (CVD). CVD is a method that uses one or more gaseous compounds or elements containing thin film elements to chemically react and generate a thin film. CVD can control the deposition thickness of the passivation material film 103 and results in a high purity of the film. In other embodiments, physical vapor deposition (PVD) can also be used to form the passivation material film.

[0091] In this embodiment, the passivation material film 103 is subjected to a second thinning treatment 109 using ion beam etching (IBE). Specifically, the process parameters for thinning the mass-loaded material film 103 using ion beam etching include: the etching gas includes Ar, the Ar gas flow rate is between 3 sccm and 7 sccm, and the chamber pressure during the etching process is e. -8 mbar to e -6 mbar.

[0092] It should be noted that in the second thinning process 109 of the passivation material film 103, the passivation material film 103 of each resonant region is thinned to the same thickness, thereby shifting the waveform of the subsequently formed filter to the right while maintaining the same bandwidth. Furthermore, the reduced surface roughness of the passivation material layer 124 after the overall thinning of the passivation material film 103 indicates improved uniformity of the thickness of each passivation material layer 124, enabling left-side frequency modulation and improving the uniformity of the left-side frequency of the filter. In this embodiment, the thickness of the passivation material film 103 removed during the second thinning process 109 is 200 to 300 angstroms.

[0093] refer to Figure 13 The passivation material layer 124 of the target resonant region is subjected to a first thinning process 113 to form a passivation layer 114.

[0094] In the filter formation method provided in this embodiment of the invention, after providing the piezoelectric stacked structure 102, a passivation material layer 124 is formed on the first electrode 104 on the second side 1052. A first thinning process 113 thins the passivation material layer 124 in the target resonant region, so that the thickness of the passivation layer 114 in the target resonant region is less than the thickness of the passivation layer 114 in other resonant regions. Because a thinner passivation layer 114 results in a higher vibration frequency, the vibration frequency of the passivation layer 114 in the target resonant region is faster than that in other resonant regions. The frequency of the resonator in the target resonant region... The rightward shift of the frequency (i.e., the increase of the high-frequency value) is beneficial for making the target resonant region a resonator with the highest vibration frequency, which corresponds to an increase in the filter bandwidth. Because the first thinning process 113 further reduces the surface roughness of the passivation layer 114 in the target resonant region, it means that the uniformity of the thickness of the passivation layer formed in the target resonant region is improved. This modulates the frequency (high-frequency value) on the right side of the filter bandwidth, improving the uniformity of the frequency on the right side of the filter bandwidth. During measurement, more frequency points will fall within the specified range, which is beneficial for improving the yield of the filter.

[0095] In this embodiment, the step of thinning the passivation material layer 124 of the working region I in the target resonant region includes: forming a passivation mask layer 108 on the passivation material layer 124, the passivation mask layer 108 exposing the target resonant region; etching the passivation material layer 124 using the passivation mask layer 108 as a mask, the remaining passivation material layer 124 serving as a passivation layer 114, the thickness of the passivation layer 114 in the target resonant region being less than the thickness of the passivation layer 114 in other resonant regions.

[0096] Specifically, the passivation mask layer 108 exposing the target resonant region refers to the working area I that exposes the target resonant region.

[0097] In this embodiment, the material of the passivation mask layer 108 includes photoresist.

[0098] It should be noted that the passivation mask layer 108 and the second mask layer are formed by exposure and development using the same photomask. That is to say, the area of ​​the mass load material layer exposed by the second mask layer is mirror-symmetrical with the area of ​​the passivation material layer 124 exposed by the passivation mask layer 108. This makes the thinning area of ​​the mass load material layer and the thinning area of ​​the passivation material layer 124 symmetrical, which is beneficial to improving the frequency stability of the resonator formed in the target resonant region, maintaining mode symmetry, enhancing anti-interference ability, and simplifying the manufacturing and integration process.

[0099] In this embodiment, during the first thinning process 113, the passivation material layer 124 of the working region I in the target resonant region is thinned. During operation, the working region I of the resonator is used to generate clock signals of various predetermined frequencies, and the thickness of the passivation layer 114 in the peripheral region II does not contribute to the generation of clock signals of various predetermined frequencies in the working region I. Accordingly, the passivation mask layer 108 only exposes the working region I of the target resonant region. In other embodiments, during the first thinning process, the passivation material layer of either the working region or the peripheral region of the target resonant region can also be thinned simultaneously.

[0100] It should be noted that the passivation material layer 124 removed during the first thinning process 113 should not be too thick or too thin. If it is removed too thickly, the passivation layer 114 in the target resonant region will be too thin, and the passivation layer 114 will not be able to protect the first electrode 104 well, resulting in reduced resonator reliability. If it is removed too thickly, the frequency increase in the high-frequency band of the filter bandwidth will not be significant, resulting in poor uniformity on the right side of the filter and poor filter yield. In this embodiment, the thickness of the passivation material layer 124 removed during the first thinning process 113 is 20 angstroms to 40 angstroms.

[0101] It should be noted that the passivation layer 114 in the target resonant region should not be too thick or too thin. If the passivation layer 114 in the target resonant region is too thin, it cannot effectively protect the first electrode 104, leading to reduced resonator reliability. If the passivation layer 114 in the target resonant region is too thick, the frequency boost in the high-frequency band of the filter's bandwidth will not be significant, resulting in poor uniformity on the right side of the filter and poor filter yield. In this embodiment, in the step of forming the passivation layer 114, the thickness of the passivation layer 114 in the target resonant region is 200 angstroms to 600 angstroms.

[0102] In this embodiment, the first thinning process 113 includes an ion beam etching (IBE) process. Specifically, the process parameters for thinning the passivation material layer 124 using ion beam etching include: the etching gas includes Ar, the Ar gas flow rate is between 3 sccm and 7 sccm, and the chamber pressure during the etching process is within e -8 mbar to e -6 mbar.

[0103] Specifically, the first thinning process 113 includes: performing an initial thinning of the passivation material layer 124 in the target resonant region; performing a thickness detection on the passivation material layer 124 after the initial thinning to obtain the thickness of the passivation material layer 124 that needs to be further thinned; and performing a second thinning of the passivation material layer 124 based on the thickness that needs to be further thinned to form the passivation layer 114.

[0104] In this embodiment, the specific steps for measuring the thickness of the passivation material layer 124 after the initial thinning and obtaining the thickness of the passivation material layer 124 that needs to be further thinned include: performing a frequency test on the passivation material layer 124 after the initial thinning, and calculating the thickness of the passivation material layer 124 that needs to be removed during the subsequent thinning process based on the frequency of the passivation material layer after the initial thinning.

[0105] It should be noted that in the first thinning process 113, the passivation material layer 124 of the working area I in the remaining resonant regions is not thinned, so the vibration frequency of the passivation layer 114 in the working area of ​​the remaining resonant regions does not change, that is, the left frequency of the filter does not change.

[0106] The method for forming the filter further includes: after forming the passivation layer 114, removing the passivation mask layer 108.

[0107] refer to Figure 14 and Figure 15 The method for forming the filter further includes: in the peripheral region II, a signal electrode is formed from one side of the first electrode 104, penetrating the first electrode 104 and the piezoelectric layer 105, and the signal electrode is located on the second electrode 106.

[0108] The signal electrode is used to connect the upper and lower electrodes. Its function is to transmit signals or excite the resonator to generate oscillations or adjust the performance of the resonator.

[0109] Specifically, the signal electrodes include a first signal electrode 118 and a second signal electrode 119 (e.g., ...). Figure 15 As shown, the signal electrode is located on the second electrode 106, so that the signal electrode and the second electrode 106 are electrically connected. When the resonator is working, the first signal electrode 118 and the second signal electrode 119 are used for signal input and output, respectively.

[0110] In this embodiment, the first signal electrode 118 and the second signal electrode 119 are made of copper. In other embodiments, the first signal electrode and the second signal electrode may also be made of other types of metallic materials.

[0111] The steps for forming signal electrodes include: Figure 14 As shown, from the side of the piezoelectric stacked structure 102 away from the second electrode 106, the first electrode 104 and the piezoelectric layer 105 in the peripheral region II are etched to form a first trench 116 and a second trench 117 exposing the second electrode 106. The first trench 116 and the second trench 117 are spaced apart. Figure 15 As shown, signal electrodes are formed on the first trench 116, the second trench 117, and a portion of the first electrode 104 layer near the first trench 116 and the second trench 117.

[0112] In this embodiment, a dry etching process is used to etch the first electrode 104 and the piezoelectric layer 105, exposing the second electrode 106 and forming the first trench 116 and the second trench 117. The dry etching process has anisotropic etching characteristics and good control over the etching profile, which is beneficial to ensuring that the morphology of the first trench 116 and the second trench 117 meets the process requirements. Furthermore, during the dry etching process, the top of the second electrode 106 and the first support layer 111 can be used as the etching stop position.

[0113] In this embodiment, the first trench 116 and the second trench 117 can be used to define the edge of the active region of the resonator, that is, the edge of the region where the resonator selects effective resonance.

[0114] It should be noted that in the steps of forming the first trench 116 and the second trench 117, the piezoelectric stacked structure 102 on the top of the first support layer 111 in the peripheral region II is also etched to form a peripheral trench 201 surrounding the working region I. The peripheral trench 201 exposes the first support layer 111. The peripheral trench 201 is farther away from the working region I than the first trench 116 and the second trench 117. The peripheral trench 201 provides space for the subsequent formation of the second support layer surrounding the piezoelectric stacked structure 102.

[0115] Continue to refer to Figure 15 The filter formation method further includes: after forming the first trench 116 and the second trench 117, and before forming the signal electrode, etching a portion of the first electrode 104 near the signal electrode to form a top air trench (TAT) 126 that penetrates the passivation layer 114 and the first electrode 104 and exposes the piezoelectric layer 105.

[0116] The top air groove 126 is used for lateral reflection of sound waves, thereby increasing the residence time of sound waves in the subsequently formed second cavity and reducing energy dissipation. This is beneficial to improving the acoustic-electric conversion performance of the resonator. In this embodiment, the top air groove 126 and the bottom air groove 125 together define the effective resonance region. Furthermore, it should be noted that only after the top air groove 126 is formed can the range of the resonator's operating vibration frequency be measured, providing a reference for frequency tuning of the first electrode 104 with a portion of its thickness in the subsequent etching working area I.

[0117] In this embodiment, the top air groove 126 is formed using a dry etching process.

[0118] It should be noted that both the first signal electrode 118 and the second signal electrode 119 have a portion located on the first electrode 104, and both are electrically connected to the first electrode 104. Since the bottoms of the first signal electrode 118 and the second signal electrode 119 are electrically connected to the second electrode 106, the first signal electrode 118 ensures that the portion of the first electrode 104 disconnected by the top air slot 126 and the second electrode 106 are at the same potential. When the resonator is working, reducing the induced potential generated by the first electrode 104 on the side of the top air slot 126 away from the working area I helps to reduce the influence of parasitic effects. Similarly, the second signal electrode 119 ensures that the portion of the second electrode 106 disconnected by the bottom air slot 125 is at the same potential as the first electrode 104. When the resonator is working, reducing the induced potential generated by the second electrode 106 on the side of the bottom air slot 125 away from the working area I helps to reduce the influence of parasitic effects.

[0119] like Figure 16 As shown, the method for forming the filter further includes: after forming the passivation layer 114, forming a second cavity 120 on the side of the first electrode 104 away from the piezoelectric layer 105.

[0120] The second cavity 120 and the first cavity in the resonator are located on both sides of the piezoelectric stack structure 102, respectively. When the resonator is working, the first cavity and the second cavity 120 play the roles of coupling, vibration amplification and tuning performance control.

[0121] Specifically, the step of forming a second cavity 120 on the side of the first electrode 104 away from the piezoelectric layer 105 includes: providing a second substrate 122; forming a second support layer 121 on the second substrate 122; and bonding the second support layer 121 to the first support layer 111 exposed in the peripheral trench 201.

[0122] The second substrate 122 can be any suitable substrate known to those skilled in the art, such as at least one of the following materials: silicon, germanium, germanium silicon, silicon carbon, silicon carbon germanium silicon, indium arsenide, gallium arsenide, indium phosphide, or other III / V compound semiconductors.

[0123] The present invention also provides a filter. (See reference) Figure 16 The diagram shows a schematic representation of the filter structure of the present invention.

[0124] The filter includes: a piezoelectric stack structure 102, the piezoelectric stack structure 102 including a piezoelectric layer 105, including a first side 1051 and a second side 1052 opposite to the first side 1051, the piezoelectric stack structure 102 also including a first electrode 104 located on the first side 1051 and a second electrode 106 located on the second side 1052; the piezoelectric stack structure 102 includes a plurality of resonant regions distributed on a plane, the resonant regions being used to form resonators, the plurality of resonant regions including a target resonant region for forming a resonator with the highest vibration frequency; a passivation layer 114 located on the first electrode 104, the thickness of the passivation layer 114 in the target resonant region being smaller than the thickness of the passivation layer 114 in the other resonant regions.

[0125] The resonator provided by this invention includes a piezoelectric stacked structure 102 in which the thickness of the passivation layer 114 in the target resonant region is smaller than that in other resonant regions. Because the thinner the passivation layer 114, the higher the vibration frequency, the vibration frequency of the passivation layer 114 in the target resonant region is faster than that in other resonant regions. The frequency of the resonator in the target resonant region shifts to the right (i.e., the high frequency value increases), which is beneficial for the target resonant region to form the resonator with the highest vibration frequency. The corresponding filter bandwidth is increased because the first thinning process further reduces the surface roughness of the passivation layer 114 in the target resonant region, which means that the thickness uniformity of the passivation layer 114 in the target resonant region is improved. This modulates the frequency (high frequency value) on the right side of the filter bandwidth, improving the uniformity of the frequency on the right side of the filter bandwidth. During measurement, more frequency points will fall within the specified range, which is beneficial for improving the yield of the filter.

[0126] Resonators with different resonant frequencies corresponding to different resonant regions are used to select a specific frequency, generate a stable oscillation signal, and provide frequency control and amplification functions.

[0127] In this embodiment, the filter includes three resonators, and the corresponding piezoelectric stack structure 102 includes three resonant regions, which are low resonant region, medium resonant region and high resonant region according to the vibration frequency of the resonators. The target resonant region is the high resonator.

[0128] It should be noted that the resonant region includes the operating region I and the peripheral region II surrounding the operating region I. The operating region I of the resonator refers to the area capable of storing and releasing energy. It is composed of energy storage elements (such as capacitors and inductors). The main function of the operating region I is to maintain oscillation, that is, to store and transfer energy, enabling the resonator to maintain stable amplitude and frequency. The peripheral region II of the resonator refers to other circuits or components connected to the resonator. The function of the peripheral region II is to provide a path for exchanging energy with the resonator.

[0129] In this embodiment, the piezoelectric stack structure 102 includes a piezoelectric layer 105, the piezoelectric layer 105 includes a first side 1051 and a second side 1052 opposite to the first side 1051, the piezoelectric stack structure 102 also includes a first electrode 104 located on the first side 1051 of the piezoelectric layer 105 and a second electrode 106 located on the second side 1052 of the piezoelectric layer 105.

[0130] The piezoelectric stack structure 102 is used to realize the mutual conversion between electrical signals and acoustic signals, so that the filter can perform filtering processing on the signals.

[0131] In this embodiment, the first electrode 104 serves as the upper electrode of the piezoelectric multilayer structure 102. The material of the first electrode 104 is a conductive material. The conductive material can be a metallic material with conductive properties, such as one or more of Mo, Al, Cu, Pt, Au, Ir, Os, Re, Pd, Rh, Ru, Mo, and W.

[0132] The piezoelectric layer 105 is made of piezoelectric material, which is a crystalline material that generates a voltage between its two ends when subjected to pressure. Piezoelectric material has a piezoelectric effect, and the piezoelectric effect of piezoelectric material can be used to realize the mutual conversion between mechanical vibration (sound wave) and alternating current, thereby realizing the conversion between sound energy and electrical energy.

[0133] In this embodiment, the second electrode 106 serves as the upper electrode of the piezoelectric multilayer structure 102. The material of the second electrode 106 is a conductive material. The conductive material can be a metallic material with conductive properties, such as one or more of Mo, Al, Cu, Pt, Au, Ir, Os, Re, Pd, Rh, Ru, Mo, and W.

[0134] The filter also includes a mass load layer 101 located on the second electrode 106 of the second side 1052.

[0135] The mass load layer 101 is used to effectively reflect the transverse modes into the working region I, effectively suppressing the transverse leakage of energy, thereby improving the Q value.

[0136] In this embodiment, the mass load layer 101 is either a continuous ring or a non-continuous ring.

[0137] It should be noted that the 1nm thick mass loading layer 101 corresponds to a frequency response of 1.8MHz to 2.2MHz. In this embodiment, the material of the mass loading layer 101 is Mo. In other embodiments, the material of the mass loading layer may also include W or Au.

[0138] In this embodiment, the thickness of the mass load layer 101 in the working region I of each of the resonant regions is different, which is determined by the design frequency of the resonator in each resonant region. Specifically, the mass load layer 101 in the high resonance region is the thinnest, the mass load layer 101 in the medium resonance region is the next thickest, and the mass load layer 101 in the low resonance region is the thickest. Correspondingly, the mass load layer 101 in the target resonance region has the smallest thickness. The vibration frequency of the mass load layer 101 with different thicknesses is different. Specifically, the thicker the mass load layer 101, the lower the resonant frequency of the resonator; the thinner the mass load layer 101, the higher the resonant frequency of the resonator. The resonators formed in the high resonance region, medium resonance region, and low resonance region have different resonant frequency regions, realizing the selection of a specific frequency. These resonators with different vibration frequencies constitute the frequency response range of the filter, i.e., the bandwidth.

[0139] It should be noted that the thickness of the mass load layer 101 in working region I is less than the thickness of the mass load layer 101 in peripheral region II. The selection of a specific frequency by the resonator and the generation of a stable oscillation signal are related to the thickness of the mass load layer 101 in working region I, but not to the thickness of the mass load layer 101 in peripheral region II. The mass load layer 101 in working region I is formed through a thinning process, and therefore is thinner than the mass load layer 101 in peripheral region II.

[0140] The filter also includes: a bottom air trench (BAT) 125, which penetrates the second electrode 106 and exposes the piezoelectric layer 105, and is located near the support layer 111. A top air trench (TAT) 126, which penetrates the first electrode 104 and exposes the piezoelectric layer 105, and is located near the signal electrode.

[0141] The bottom air slot 125 is used for lateral reflection of sound waves, which helps to increase the residence time of sound waves in the cavity, thereby reducing energy dissipation and improving the acoustic-electric conversion performance of the resonator. The top air slot 126 is also used for lateral reflection of sound waves, thereby increasing the residence time of sound waves in the second cavity 120, further reducing energy dissipation and improving the acoustic-electric conversion performance of the resonator. In this embodiment, the top air slot 126 and the bottom air slot 125 together define the effective resonance region.

[0142] It should be noted that an edge protrusion structure 131 (Frame) surrounding the effective resonant region in the working region I is also formed on the second electrode 106, which is used to change the acoustic impedance of the edge, prevent energy leakage from the working region I, and improve the quality factor of the resonator.

[0143] In this embodiment, the material of the edge protrusion structure 131 is different from the material of the second electrode 106. In other embodiments, the material of the edge protrusion structure can also be the same as the material of the second electrode. When the edge protrusion structure and the second electrode are made of the same material, the edge protrusion structure and the second electrode can be formed by etching the same material, and the corresponding edge protrusion structure and the second electrode are an integral structure.

[0144] The filter further includes: a first cavity 115 located on the side of the second electrode 106 away from the piezoelectric layer 105, and the first substrate 112, the second electrode 106, and the first support layer 111 forming the first cavity 115.

[0145] The first cavity 115 helps reduce the vibration energy loss of the resonator and can improve the acoustic-electric conversion performance of the resonator.

[0146] In this embodiment, the materials of the passivation layer 114 and the mass load layer 101 have different frequency variations, i.e., different frequency response characteristics. The ratio of the frequency response coefficients of the mass load layer 101 and the passivation layer 114 of the same thickness is 4 to 6.66.

[0147] As an example, the 1nm thick mass loading layer 101 corresponds to a frequency response of 1.8MHz to 2.2MHz. The 1nm thick passivation layer 114 corresponds to a frequency response of 0.3MHz to 0.5MHz. Specifically, the passivation layer 114 is made of silicon nitride.

[0148] It should be noted that the passivation layer 114 in the target resonant region should not be too thick or too thin. If the passivation layer 114 in the target resonant region is too thin, it cannot adequately protect the first electrode 104, leading to reduced resonator reliability. If the passivation layer 114 in the target resonant region is too thick, the frequency boost in the high-frequency band of the filter's bandwidth will not be significant, resulting in poor uniformity on the right side of the filter and poor filter yield. In this embodiment, the thickness of the passivation layer 114 in the target resonant region is 200 angstroms to 600 angstroms.

[0149] It should be noted that the thickness difference between the passivation layer 114 of the target resonant region and the passivation layer 114 of other resonant regions should not be too large or too small. If the thickness difference is too large, the passivation layer 114 of the target resonant region will be too thin, and the passivation layer 114 will not be able to protect the first electrode 104 well, resulting in reduced resonator reliability. If the thickness difference is too small, the passivation layer 114 of the target resonant region will be too thick, resulting in insignificant frequency boost in the high-frequency band of the filter bandwidth, poor uniformity on the right side of the filter, and poor filter yield. In this embodiment, the thickness difference between the passivation layer 114 of the target resonant region and the passivation layer 114 of other resonant regions is 20 angstroms to 40 angstroms.

[0150] It should also be noted that the thickness of the passivation layer 114 in the working region I of the target resonant region is less than the thickness of the passivation layer 114 in the peripheral region II of the target resonant region, while the thickness of the passivation layer 114 in the peripheral region II of the target resonant region is the same as the thickness of the passivation layer 114 in other resonant regions. During operation, the working region I of the resonator is used to generate clock signals of various predetermined frequencies, and the thickness of the passivation layer 114 in the peripheral region II does not contribute to the generation of clock signals of various predetermined frequencies in the working region I.

[0151] The resonator further includes a signal electrode extending from one side of the first electrode 104, penetrating the first electrode 104 and the piezoelectric layer 105 in the peripheral region II. The bottom of the signal electrode is located on the second electrode 106, and the signal electrode is spaced apart from the second support layer 121. Specifically, the signal electrode includes a first signal electrode 118 and a second signal electrode 119, which are located on the second electrode 106, such that the signal electrode and the second electrode 106 are electrically connected. When the resonator is working, the first signal electrode 118 and the second signal electrode 119 are used for signal input and output, respectively.

[0152] The signal electrode is used to connect the upper and lower electrodes. Its function is to transmit signals or excite the resonator to generate oscillations or adjust the performance of the resonator.

[0153] In this embodiment, both the first signal electrode 118 and the second signal electrode 119 have a portion located on the first electrode 104. Correspondingly, both the first signal electrode 118 and the second signal electrode 119 are electrically connected to the first electrode 104. Since the bottoms of the first signal electrode 118 and the second signal electrode 119 are electrically connected to the second electrode 106, the first signal electrode 118 ensures that the portion of the first electrode 104 disconnected by the top air slot 126 and the second electrode 106 are at the same potential. When the resonator is working, this reduces the induced potential generated by the first electrode 104 on the side of the top air slot 126 that is far from the working area I, which helps to reduce the influence of parasitic effects. Similarly, the second signal electrode 119 ensures that the portion of the second electrode 106 disconnected by the bottom air slot 125 is at the same potential as the first electrode 104. When the resonator is working, this reduces the induced potential generated by the second electrode 106 on the side of the bottom air slot 125 that is far from the working area I, which helps to reduce the influence of parasitic effects.

[0154] In this embodiment, the first signal electrode 118 and the second signal electrode 119 are made of copper. In other embodiments, the first signal electrode and the second signal electrode may also be made of other types of metallic materials.

[0155] The filter further includes a second cavity 120 located on the side of the first electrode 104 away from the piezoelectric layer 105, the second cavity being surrounded by two support layers 121 and a second substrate 122.

[0156] The second cavity 120 and the first cavity 115 in the resonator are located on both sides of the piezoelectric stack structure 102, respectively. When the resonator is working, the first cavity and the second cavity 115 play the roles of coupling, vibration amplification and tuning performance control.

[0157] The second substrate 122 can be any suitable substrate known to those skilled in the art, such as at least one of the following materials: silicon, germanium, germanium silicon, silicon carbon, silicon carbon germanium silicon, indium arsenide, gallium arsenide, indium phosphide, or other III / V compound semiconductors.

[0158] The filter in this embodiment of the invention can be formed using the filter formation method described in the foregoing embodiment, or it can be formed using other filter formation methods, which will not be described again in this embodiment.

[0159] Accordingly, embodiments of the present invention also provide an electronic device, which includes the filter of the foregoing embodiments.

[0160] Filters can be integrated into various electronic devices. As the foregoing analysis shows, filters have high reliability, which in turn enables the development of highly reliable electronic devices. These electronic devices can include personal computers, smartphones and other mobile terminals, media players, navigation devices, video game consoles, game controllers, tablet computers, wearable devices, security access control systems, POS terminals, medical devices, flight simulators, and more.

[0161] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method of forming a filter, characterized by, The application relates to a filter and a forming method thereof. Providing a piezoelectric laminated structure, the piezoelectric laminated structure comprising a piezoelectric layer, the piezoelectric layer comprising a first side and a second side opposite to the first side, the piezoelectric laminated structure further comprising a first electrode on the first side and a second electrode on the second side; the piezoelectric laminated structure comprises a plurality of resonant regions distributed on a plane, the resonant regions are used for forming resonators, and the plurality of resonant regions comprise high resonant regions, medium resonant regions and low resonant regions, wherein a resonant region used for forming a resonator with the highest vibration frequency is a target resonant region; the thickness of a mass load layer of a working region in each resonant region is different, wherein the thicker the mass load layer is, the lower the resonant frequency of the resonator is; the thickness of the mass load layer of the working region in the target resonant region is greater than an expected thickness, and the difference between the thickness of the mass load layer of the working region in the target resonant region and the expected thickness is greater than a fluctuation error of an etching machine; forming a passivation material layer covering the first electrode on the first side; performing a first thinning treatment on the passivation material layer of the target resonant region to form a passivation layer, so that the thickness of the passivation layer of the target resonant region is less than the thickness of the passivation layer in other resonant regions; wherein the step of forming the passivation material layer covering the first electrode on the first side comprises: forming a passivation material film covering the first electrode on the first side; and performing a second thinning treatment on the passivation material film to form the passivation material layer.

2. The method of forming a filter according to claim 1, wherein, The thickness of the passivation material layer removed in the first thinning treatment is 20 angstroms to 40 angstroms.

3. The method of claim 1, wherein the filter is a low-pass filter. In the step of forming the passivation layer, the thickness of the passivation layer of the target resonant region is 200 angstroms to 600 angstroms.

4. The method of claim 1, wherein the filter is a low-pass filter. The first thinning treatment includes an ion beam etching process, and process parameters of the ion beam etching process include: an etching gas including Ar, a gas flow of the Ar being 3sccm to 7sccm, a chamber pressure during etching being e -8 -0.1mbar to e -6 -0.1mbar.

5. The method of claim 1, wherein the filter is a low-pass filter. The step of the first thinning treatment comprises: performing a preliminary thinning on the passivation material layer of the target resonant region; detecting the thickness of the passivation material layer after the preliminary thinning to obtain the thickness of the passivation material layer which needs to be continuously thinned; performing a re-thinning on the passivation material layer according to the thickness which needs to be continuously thinned to form the passivation layer.

6. The method of claim 1, wherein the filter is a low-pass filter. The resonant region comprises a working region and a peripheral region surrounding the working region; In the process of the first thinning treatment, the passivation material layer of the working region in the target resonant region is thinned.

7. The method of claim 1, wherein the filter is a low-pass filter. The resonant region comprises a working region and a peripheral region surrounding the working region; The forming method of the filter further comprises: forming a mass load layer on the second electrode from the second side.

8. The method of claim 7, wherein the filter is formed by a process comprising: The forming method of the filter further comprises: providing an expected thickness of the mass load layer of the working region in the target resonant region.

9. The method for forming a filter as described in claim 8, characterized in that, The ratio of the frequency change rate of the mass load layer to the passivation layer is 4 to 6.

66.

10. The method of claim 8, wherein the filter is formed by a process selected from the group consisting of a photolithography process, a laser drilling process, a mechanical drilling process, and a chemical etching process. The difference between the thickness of the mass load layer of the working region in the target resonant region and the expected thickness is 20 angstroms to 40 angstroms.

11. The method of claim 7, wherein the filter is formed by a process comprising: The step of forming a mass load layer on the second electrode from the second side comprises: forming a mass load material layer on the second electrode from the second side; respectively thinning the mass load material layer of the working region in each resonant region to form the mass load layer with different thicknesses.

12. The method of claim 1, wherein the filter is a surface acoustic wave filter. The method for forming the filter further comprises: forming a first cavity on the side of the second electrode facing away from the piezoelectric layer before forming the passivation material layer; forming a second cavity on the side of the first electrode facing away from the piezoelectric layer after forming the passivation layer.

13. The method of claim 1, wherein the filter is a surface acoustic wave filter. The material of the passivation layer comprises silicon nitride.

14. A filter, characterized by The method comprises: The piezoelectric stack structure comprises a piezoelectric layer, a first side and a second side opposite to the first side, a first electrode on the first side, and a second electrode on the second side; the piezoelectric stack structure comprises a plurality of resonant regions distributed on a plane, the resonant regions are used to form resonators, and the resonant regions comprise high resonant regions, medium resonant regions, and low resonant regions; the resonant region used to form a resonator with the highest vibration frequency is a target resonant region; the thickness of a mass load layer in an operating region in each resonant region is different, and the thicker the mass load layer, the lower the resonant frequency of the resonator; the thickness of the mass load layer in the operating region in the target resonant region is greater than an expected thickness, and the difference between the thickness of the mass load layer in the operating region in the target resonant region and the expected thickness is greater than a fluctuation error of an etching machine; a passivation layer on the first electrode, the thickness of the passivation layer in the target resonant region is less than the thickness of the passivation layer in other resonant regions.

15. The filter of claim 14, wherein, The thickness of the passivation layer in the target resonant region is 200 angstroms to 600 angstroms.

16. The filter of claim 14, wherein, The difference between the thickness of the passivation layer in the target resonant region and the thickness of the passivation layer in other resonant regions is 20 angstroms to 40 angstroms.

17. The filter of claim 14, wherein, The material of the passivation layer comprises silicon nitride.

18. The filter of claim 14, wherein, The mass load layer is on the second electrode on the second side.

19. The filter of claim 18, wherein, The ratio of the frequency response coefficient of the mass load layer with the same thickness to the frequency response coefficient of the passivation layer with the same thickness is 4 to 6.

66.

20. The filter of claim 14, wherein, The filter further comprises: a first cavity on the side of the second electrode facing away from the piezoelectric layer; a second cavity on the side of the first electrode facing away from the piezoelectric layer.

21. An electronic device, comprising: The filter comprises any one of claims 14 to 20.

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