Filter, forming method thereof and electronic equipment

Abstract

The invention discloses a filter and a forming method thereof, and electronic equipment, and the method comprises the steps: carrying out the thinning of a passivation material layer in a target resonance region through first thinning processing after a piezoelectric laminated structure is provided, so as to enable the thickness of a passivation layer in the target resonance region to be smaller than the thickness of passivation layers in other resonance regions, therefore, the vibration frequency of the passivation layer of the target resonance area is faster than that of the passivation layer of other resonance areas, the frequency of the resonator of the target resonance area shifts rightwards, the target resonance area is used for forming the resonator with the highest vibration frequency, the bandwidth of the corresponding filter is increased, and the bandwidth of the filter is increased. The surface roughness of the passivation layer in the target resonance area is further reduced through the first thinning treatment, which means that the thickness uniformity of the passivation layer in the target resonance area is improved, so that the right side frequency of the filter bandwidth is modulated, the uniformity of the right side frequency of the filter bandwidth is improved, and the filter performance is improved. And during measurement, more frequency points fall within the range of specification requirements, so that the yield of the filter can be improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductors, and in particular to a filter and a forming method thereof, and electronic equipment. Background Art

[0002] Since analog RF communication technology was developed in the early 1990s, RF front-end modules have gradually become the core components of communication equipment. Among all RF front-end modules, filters have become the components with the strongest growth momentum and the greatest development prospects. With the rapid development of wireless communication technology and the increasing maturity of 5G communication protocols, the market has also put forward more stringent standards for the performance of RF filters in all aspects. The performance of the filter is determined by the resonator units that make up the filter. Among the existing filters, the film bulk acoustic resonator (FBAR) has become one of the most suitable filters for 5G applications due to its small size, low insertion loss, large out-of-band suppression, high quality factor, high operating frequency, large power capacity and good anti-static shock ability.

[0003] Generally, a thin film bulk acoustic wave resonator includes two thin film electrodes, and a piezoelectric thin film layer is arranged between the two thin film electrodes. The thin film electrodes and the piezoelectric thin film layer are used as a piezoelectric laminate structure. Its working principle is to utilize the piezoelectric thin film layer to generate vibrations under an alternating electric field. The vibration excites a bulk acoustic wave that propagates along the thickness direction of the piezoelectric thin film layer. The sound wave is reflected back when it reaches the interface between the upper and lower electrodes and the air, and then reflects back and forth inside the film to form an oscillation. When the sound wave propagates in the piezoelectric thin film layer at an odd multiple of half the wavelength, a standing wave oscillation is formed.

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

[0005] However, FBAW cannot meet the requirements of high-performance RF systems. Summary of the invention

[0006] The problem solved by the present invention is to provide a filter and a forming method thereof, and an electronic device, so as to improve the performance of the filter.

[0007] To solve the above problems, the present invention provides a method for forming a filter, comprising: providing a piezoelectric stack structure, the piezoelectric stack structure comprising a piezoelectric layer, the piezoelectric layer comprising 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 comprising a plurality of resonance regions distributed on a plane, the resonance regions being used to form a resonator, the plurality of resonance regions comprising a target resonance region for forming a resonator with the highest vibration frequency; forming a passivation material layer covering the first electrode on the first side; performing a first thinning process on the passivation material layer in the target resonance region to form a passivation layer.

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

[0009] Correspondingly, the present invention also provides an electronic device, comprising the aforementioned filter.

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

[0011] In a method for forming a filter provided in an embodiment of the present invention, a piezoelectric stack structure is provided, wherein 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 resonance zones, the resonance zones are used to form a resonator, and the plurality of resonance zones include a target resonance zone for forming a resonator with the highest vibration frequency. After providing the piezoelectric stack structure, a passivation material layer is formed on the first electrode on the second side. The first thinning treatment thins the passivation material layer in the target resonance area, so that the thickness of the passivation layer in the target resonance area is less than the thickness of the passivation layer in other resonance areas. Because the thinner the passivation layer thickness is, the higher the vibration frequency is, so the vibration frequency of the passivation layer in the target resonance area is faster than the vibration frequency of the passivation layer in other resonance areas. The frequency of the resonator in the target resonance area is shifted to the right (that is, the high frequency value increases), which is conducive to using the target resonance area to form the resonator with the highest vibration frequency. The corresponding filter bandwidth is manifested as an increase in the bandwidth of the filter, because the first thinning treatment further reduces the surface roughness of the passivation layer in the target resonance area, which means that the thickness uniformity of the passivation layer formed in the target resonance area is improved, so that the frequency on the right side of the filter bandwidth (high frequency value) is modulated, which improves the uniformity of the frequency on the right side of the filter bandwidth. During measurement, more frequency points will fall within the range of specification requirements, which is conducive to improving the yield of the filter.

[0012] A filter provided by an embodiment of the present invention includes a piezoelectric stack structure, 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 resonance zones, the resonance zones are used to form a resonator, and the plurality of resonance zones include a target resonance zone for forming a resonator with the highest vibration frequency. The thickness of the passivation layer in the target resonance area is smaller than the thickness of the passivation layer in other resonance areas. Because the thinner the thickness of the passivation layer, the higher the vibration frequency, the vibration frequency of the passivation layer in the target resonance area is faster than that of the passivation layer in other resonance areas. The frequency of the resonator in the target resonance area is shifted to the right (that is, the high frequency value increases), which is conducive to using the target resonance area to form the resonator with the highest vibration frequency. The corresponding filter bandwidth is manifested as an increase in the bandwidth of the filter, because the first thinning treatment further reduces the surface roughness of the passivation layer in the target resonance area, which means that the thickness uniformity of the passivation layer in the target resonance area is improved, so that the frequency on the right side of the filter bandwidth (high frequency value) is modulated, thereby improving the uniformity of the frequency on the right side of the filter bandwidth. During measurement, more frequency points will fall within the range of specification requirements, which is conducive to improving the yield of the filter. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0014] Figures 5 to 16 It is a structural schematic diagram corresponding to each step in the method for forming the filter of the present invention. DETAILED DESCRIPTION

[0015] As can be seen from the background technology, currently, Film Bulk Acoustic Resonator (FBAR) is widely used. Now, the reasons for the poor performance of the device are analyzed in combination with a method for forming a filter.

[0016] A method for forming a filter includes: Figure 1 As shown, a piezoelectric stack structure is provided, wherein the piezoelectric stack structure includes a plurality of resonance regions ( Figure 1 Only one resonance zone is shown in the figure, the resonance zone includes a working area I and a peripheral area II surrounding the working area 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 load material layer (not shown in the figure) is formed on the first electrode 2 from the first side; a photoresist layer 7 is formed on the mass load material layer; the photoresist layer 7 is used as a mask to thin the mass load material layer in the working area I to form a mass load layer 3. Usually, an etching machine is used to thin the mass load 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 a passivation layer 6.

[0020] The frequency modulation process of the existing filter includes thinning the mass load material layer of multiple resonance zones to different thicknesses respectively, so that the thickness of the mass load layer 3 of the working zone I in each resonance zone is different, so as to obtain a specific bandwidth of the filter; the passivation material layer 5 of multiple resonance zones is thinned in the same way to adjust the frequency, so that the filter bandwidth reaches the target frequency band, and the uniformity of the frequency (low frequency value) on the left side of the filter bandwidth is improved. It is now found that in the process of thinning the mass load material layer of the working zone I, due to abnormal conditions such as fluctuations in the etching machine, the thinning thickness of the mass load material layer of each working zone I is different from the expected thinning thickness, so that the frequency (high frequency value) on the right side of the filter bandwidth fluctuates, and the uniformity of the frequency on the right side does not meet the requirements, which will lead to a low filter qualification rate.

[0021] In the method for forming a filter provided in an embodiment of the present invention, a piezoelectric stack structure is provided, wherein 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 resonance zones, the resonance zones are used to form a resonator, and the plurality of resonance zones include a target resonance zone for forming a resonator with the highest vibration frequency. After providing the piezoelectric stack structure, a passivation material layer is formed on the first electrode on the second side. The first thinning treatment thins the passivation material layer in the target resonance area, so that the thickness of the passivation layer in the target resonance area is less than the thickness of the passivation layer in other resonance areas. Because the thinner the passivation layer thickness is, the higher the vibration frequency is, so the vibration frequency of the passivation layer in the target resonance area is faster than the vibration frequency of the passivation layer in other resonance areas. The frequency of the resonator in the target resonance area is shifted to the right (that is, the high frequency value increases), which is conducive to using the target resonance area to form the resonator with the highest vibration frequency. The corresponding filter bandwidth is manifested as an increase in the bandwidth of the filter, because the first thinning treatment further reduces the surface roughness of the passivation layer in the target resonance area, which means that the thickness uniformity of the passivation layer formed in the target resonance area is improved, so that the frequency on the right side of the filter bandwidth (high frequency value) is modulated, which improves the uniformity of the frequency on the right side of the filter bandwidth. During measurement, more frequency points will fall within the range of specification requirements, which is conducive to improving the yield of the filter.

[0022] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0023] Figures 5 to 16 It is a structural schematic diagram corresponding to each step in the method for forming the filter of the present invention.

[0024] refer to Figure 5, providing a piezoelectric stacked structure 102, the piezoelectric stacked structure 102 includes a plurality of resonance regions distributed on a plane, the resonance regions are used to form a resonator, the plurality of resonance regions include a target resonance region ( Figure 5 Only the target resonance region is shown in FIG.

[0025] Different resonance regions are used to form corresponding resonators with different resonance frequencies. The resonator is 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 stacked structure 102 includes three resonance zones, which are a low resonance zone, a middle resonance zone and a high resonance zone according to the vibration frequency of the resonator to be formed, and the target resonance zone is a high resonator.

[0027] It should be noted that the resonance area includes a working area I and a peripheral area II surrounding the working area I. The working area I of the resonator refers to the area that can store and release energy. It is composed of energy storage elements (such as capacitors and inductors). The main function of the working area I is to maintain oscillation, that is, to store and transfer energy so that the resonator can maintain the stability of amplitude and frequency. The peripheral area II of the resonator refers to other circuits or components connected to the resonator. The function of the peripheral area 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, and 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 stacked structure 102 provides preparation for the subsequent formation of a resonator. The corresponding piezoelectric stacked structure 102 is used to realize the mutual conversion between the electrical signal and the acoustic signal, so that the filter performs filtering processing on the signal.

[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 may be a metal material having conductive properties, for example, one or more of Mo, Al, Cu, Pt, Au, Ir, Os, Re, Pd, Rh, Ru, Mo and W.

[0032] The material of the piezoelectric layer 105 is a piezoelectric material, which is a crystalline material that will generate a voltage between the two end faces when subjected to pressure. The piezoelectric material has a piezoelectric effect. The piezoelectric effect of the piezoelectric material can realize the mutual conversion of mechanical vibration (sound wave) and alternating current, thereby realizing the conversion of sound energy and electrical energy. The material of the piezoelectric layer 105 can be a piezoelectric material with a wurtzite crystal structure such as ZnO, AlN, GaN, aluminum zirconate titanate or lead titanate. In this embodiment, the material of the piezoelectric layer 105 is AlN. In this embodiment, the piezoelectric layer 105 can be formed by a deposition process such as a chemical vapor deposition process (CVD), a physical vapor deposition process (PVD) or an atomic layer deposition process (ALD).

[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 may be a metal material having conductive properties, for example, one or more of 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 a temporary substrate 100 .

[0036] In this embodiment, the temporary substrate 100 may be any suitable semiconductor substrate, such as a bulk silicon substrate, and may 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 for 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 serves 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. In the subsequent process of removing the temporary substrate 100, the first buffer layer also serves as a stop layer, which helps to prevent the subsequent process of removing the temporary substrate 100 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 by a deposition process, such as a chemical vapor deposition process or an atomic layer deposition process.

[0040] refer to Figure 6 and Figure 7 The filter forming method 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 mode to the working area I, effectively suppressing the transverse leakage of energy, so as to achieve the purpose of improving the Q value.

[0042] In this embodiment, the mass loading layer 101 is in a continuous ring shape or a discontinuous ring shape.

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

[0044] It should be noted that the thickness of the mass load layer 101 in the working area I in each of the resonance zones is different. Specifically, the mass load layer 101 in the high resonance zone is the thinnest, followed by the mass load layer 101 in the middle resonance zone, and the mass load layer 101 in the low resonance zone is the thickest. Correspondingly, the mass load layer 101 in the target resonance zone has the smallest thickness. The vibration frequencies of mass load layers 101 of different thicknesses are different. Specifically, the thicker the mass load layer 101, the lower the resonance frequency of the resonator, and the thinner the mass load layer 101, the larger the resonance frequency of the resonator. The resonators formed by the high resonance zone, the middle resonance zone and the low resonance zone have different resonance frequency regions, which realizes the selection of specific frequencies. These resonators with different vibration frequencies constitute the frequency response range of the filter, that is, the bandwidth.

[0045] Specifically, the step of forming the mass load layer 101 on the second electrode 106 from the second side 1052 includes: forming a mass load material layer 123 (such as Figure 6 ); forming a mass load mask layer 107 (as shown in the mass load material layer 123); Figure 6 As shown); using the mass load mask layer 107 as a mask, etching the mass load material layer 123 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 in each of the resonance zones is thinned to different thicknesses, so that the remaining thicknesses of the mass load material layer 123 in different resonance zones are different, thereby forming the mass load layer 101.

[0048] In this embodiment, the number of resonance zones is three. In the process of thinning the mass load layer 101 of different resonance zones 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 to cover the middle resonance zone and the high resonance zone and expose the low resonance zone, and the mass load material layer 123 of the low resonance zone is thinned by the first mask layer; a second mask layer (not shown in the figure) is formed to cover the middle resonance zone and the low resonance zone and expose the high resonance zone, and the mass load material layer 123 of the high resonance zone is thinned by the second mask layer; a third mask layer is formed to cover the low resonance zone and the high resonance zone and expose the middle resonance zone, and the mass load material layer 123 of the middle resonance zone is thinned by the third mask layer.

[0049] It should be noted that the thinning process of the mass load material layer 123 in each resonance zone is performed on the mass load material layer 123 in the working area I of each resonance zone. In other embodiments, the mass load material layer in the working area and the peripheral area may also be thinned at the same time.

[0050] As an example, the thinned thickness of the mass load material layer 123 in the high resonance zone is 600 angstroms to 700 angstroms, the thinned thickness of the mass load material layer 123 in the middle resonance zone is 500 angstroms to 600 angstroms, and the thinned thickness of the mass load material layer 123 in the low resonance zone is 300 angstroms to 400 angstroms.

[0051] In this embodiment, a chemical vapor deposition process or a physical vapor deposition process is used to form the mass load material layer 123. In other embodiments, in order to improve the density of the mass load layer, an atomic layer deposition process may be used to form the mass load material layer.

[0052] In this embodiment, an ion beam etching (IBE) process is used to thin the mass load material layer 123 .

[0053] It should be noted that the etching machine 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 is also getting smaller and smaller, and the fluctuation error of the etching machine has an increasingly greater impact on the thickness of the mass load layer 101.

[0054] Therefore, in order to cope with the influence of the fluctuation error of the etching machine on the thickness of the mass load layer 101, the method for forming the filter also includes: providing an expected thickness of the mass load layer 101 in the working area I in the target resonance area; 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 area I in the target resonance area is greater than the expected thickness.

[0055] It should be noted that the method for forming the filter further includes: after providing the piezoelectric stacked 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 resonance region to form a passivation layer. The thickness of the mass load layer 101 in the working area I in the target resonance 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 resonance zone 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 in the target resonance zone 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 area I in the target resonance area and the expected thickness should not be too large or too small. If the difference is too large, the thickness required for the subsequent first thinning treatment of the passivation material layer will be too large, and the first thinning treatment of the passivation material layer in the target resonance area will take too much process time and cost. If the difference is too small, that is, the thinning margin provided by the subsequent first thinning treatment of the passivation material layer is too small, strict requirements are placed on the control ability of the etching process of the passivation material layer, otherwise the thickness of the formed passivation layer may be too thin, resulting in the detection frequency band of the filter not meeting the design requirements. In this embodiment, the difference between the thickness of the mass load layer 101 in the working area I in the target resonance area 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, and the thinning thickness value for the subsequent second thinning treatment of the passivation material film is pre-designed, so that the thickness of the formed passivation material layer is within an appropriate range, so that 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 forming method further includes: after forming the mass load layer 101, etching the second electrode 106 in the edge area of ​​the working area I to form a bottom air trench (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 using the shielding layer as a mask to form the bottom air groove 125 exposing the piezoelectric layer 105.

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

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

[0064] In this embodiment, the second electrode 106 is etched by dry etching process using the blocking layer as a mask 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, so that the bottom air groove 125 has better controllability of the etching profile, which is conducive to making the morphology of the bottom air groove 125 meet the process requirements.

[0065] The method for forming the resonator further 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 using the shielding layer as a mask, the edge area of ​​the peripheral region II in the second electrode 106 is also etched using the shielding layer as a mask, so as to separate the second electrodes 106 in different resonance regions.

[0067] Continue to refer Figure 8 The method for forming the resonator further includes: after forming the bottom air groove 125 , forming a first supporting layer 111 covering the peripheral area II and exposing the second electrode 106 in the working area I from one side of the second electrode 106 .

[0068] The first supporting layer 111 is prepared for subsequent bonding of the first substrate.

[0069] In this embodiment, the first supporting layer 111 has a first opening 110 , and the first opening 110 exposes the second electrode 106 in the working area I.

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

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

[0072] It should be noted that the method for forming the resonator also includes: after forming the bottom air groove 125, forming a protective layer (not shown in the figure) on the end surface 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 is used to prepare for the subsequent bonding of the first substrate to the end face of the first support layer 111 away from the piezoelectric stack structure 102. The protective layer is also used to isolate the second electrode 106 exposed by the first opening 110 from external water vapor, so that the surface of the second electrode 106 is not easily oxidized, which is beneficial to improving the reliability of the resonator performance and enabling the resonator to meet the requirements of high-performance RF systems. In addition, because of the protective layer, when the resonator is working, as the working temperature increases, the vibration frequency of the protective layer increases, which can compensate for the decrease in the vibration frequency of the piezoelectric layer 105 to a certain extent, which is beneficial to prevent the vibration frequency of the piezoelectric stack structure 102 and the protective layer as a whole from decreasing too much, which is beneficial to achieving the effect of improving the temperature drift coefficient of the piezoelectric resonator and improving the reliability of the resonator performance.

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

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

[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 material of the edge protrusion structure and the second electrode is the same, 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 integrated structure.

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

[0078] The first cavity 115 is beneficial to reducing the vibration energy loss of the resonator and can improve the acoustic-to-electric conversion performance of the resonator.

[0079] Specifically, the step of forming the first cavity 115 includes: providing a first substrate 112 ; bonding the first substrate 112 on the first support layer 111 , wherein the first substrate 112 , the second electrode 106 , and the first support layer 111 enclose the first cavity 115 .

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

[0081] It should be noted that the first substrate 112 is bonded to the protective layer on the first supporting layer 111 , and the contact surface between the protective layer and the first substrate 112 is bonded by a covalent bond of Si—O—Si.

[0082] refer to Fig.10 The filter forming method further includes: removing the temporary substrate 100 and the first buffer layer after forming the first cavity 115. 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 processes is used to remove the first buffer layer.

[0084] refer to Fig.11 and Fig.12 , a passivation material layer 124 (such as Fig.12 shown).

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

[0086] The material of the passivation material layer 124 and the material of the mass load layer 101 correspond to different frequency changes, that is, 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 corresponding to the passivation material layer 124 with a thickness of 1 nm is 0.3 MHz to 0.5 MHz. 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: Fig.11 As shown, a passivation material film 103 covering the first electrode 104 is formed on the first side 1051; Fig.12 As shown, the passivation material film 103 is subjected to 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 passivation material film 103 is formed to a thickness of 300 angstroms to 1000 angstroms.

[0090] In this embodiment, the passivation material film 103 is formed by a chemical vapor deposition process. The chemical vapor deposition process is a method of generating a thin film by chemically reacting one or more gas phase compounds or simple substances containing thin film elements. The chemical vapor deposition process can control the deposition thickness of the passivation material film 103 and make the film purity of the passivation material film 103 higher. In other embodiments, the passivation material film can also be formed by a physical vapor deposition process.

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

[0092] It should be noted that in the step of performing the second thinning treatment 109 on the passivation material film 103, the passivation material film 103 in each resonance zone is performed, so that the passivation material film 103 in each resonance zone in the filter is thinned by the same thickness as a whole, so that the waveform of the filter formed subsequently is shifted to the right as a whole, and the bandwidth of the filter remains unchanged; in addition, the surface roughness of the passivation material layer 124 obtained after the overall thinning of the passivation material film 103 is reduced, which means that the thickness uniformity of each passivation material layer 124 is improved, so that the filter realizes left-side frequency modulation, and improves the uniformity of the frequency on the left side of the filter. In this embodiment, during the process of performing the second thinning treatment 109 on the passivation material film 103, the thickness of the passivation material film 103 removed is 200 angstroms to 300 angstroms.

[0093] refer to Fig.13 , performing a first thinning process 113 on the passivation material layer 124 of the target resonance area to form a passivation layer 114 .

[0094] In the method for forming a filter provided in an embodiment of the present invention, after providing a piezoelectric stacked structure 102, a passivation material layer 124 is formed on the first electrode 104 on the second side 1052, and a first thinning process 113 is performed to thin the passivation material layer 124 in the target resonance region, so that the thickness of the passivation layer 114 in the target resonance region is less than the thickness of the passivation layer 114 in other resonance regions. Because the thinner the thickness of the passivation layer 114, the higher the vibration frequency, the vibration frequency of the passivation layer 114 in the target resonance region is faster than the vibration frequency of the passivation layer 114 in other resonance regions, and the frequency of the resonator in the target resonance region is faster than that of the passivation layer 114 in other resonance regions. The rate shifts to the right (i.e., the high frequency value increases), which is beneficial for the target resonance area to be used to form a resonator with the highest vibration frequency, and the corresponding filter bandwidth is manifested as an increase in the bandwidth of the filter; because the first thinning treatment 113 further reduces the surface roughness of the passivation layer 114 in the target resonance area, it means that the thickness uniformity of the passivation layer formed in the target resonance area is improved, so that the frequency on the right side of the filter bandwidth (high frequency value) is modulated, thereby improving the uniformity of the frequency on the right side of the filter bandwidth. When measuring, more frequency points will fall within the range of specification requirements, which is beneficial to improving the yield of the filter.

[0095] In this embodiment, the step of thinning the passivation material layer 124 in the working area I in the target resonance area includes: forming a passivation mask layer 108 on the passivation material layer 124, and the passivation mask layer 108 exposes the target resonance area; etching the passivation material layer 124 using the passivation mask layer 108 as a mask, and the remaining passivation material layer 124 serves as the passivation layer 114, and the thickness of the passivation layer 114 in the target resonance area is less than the thickness of the passivation layer 114 in other resonance areas.

[0096] Specifically, the target resonance region exposed by the passivation mask layer 108 refers to the working region I where the target resonance region is exposed.

[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, 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, so that the thinned area of ​​the mass-load material layer and the thinned area of ​​the passivation material layer 124 are symmetrical, which is beneficial to improving the frequency stability of the resonator formed in the target resonance area, maintaining the mode symmetry, enhancing the 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 in the working area I of the target resonance area is thinned. During operation, the working area 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 area II is not helpful for the working area I to generate clock signals of various predetermined frequencies. Accordingly, the passivation mask layer 108 only exposes the working area I of the target resonance area. In other embodiments, during the first thinning process, the passivation material layer in the working area or the peripheral area of ​​the target resonance area can also be thinned at the same time.

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

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

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

[0103] Specifically, the steps of the first thinning treatment 113 include: performing initial thinning on the passivation material layer 124 of the target resonance area; performing 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 thinning the passivation material layer 124 again according to the thickness that needs to be further thinned to form the passivation layer 114.

[0104] In this embodiment, the thickness of the passivation material layer 124 after the initial thinning is detected, and the specific steps of 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 second thinning process according to the frequency of the passivation material layer after the initial thinning.

[0105] It should be noted that in the step of the first thinning treatment 113, the passivation material layer 124 of the working area I in the remaining resonance areas is not thinned, so that the vibration frequency of the passivation layer 114 in the working area in the remaining resonance areas does not change, that is, the left side frequency of the filter does not change.

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

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

[0108] The signal electrode is used to connect the upper electrode and the lower electrode, and its function is to transmit a signal or excite the resonator to generate oscillation or adjust the performance of the resonator.

[0109] Specifically, the signal electrode includes a first signal electrode 118 and a second signal electrode 119 (eg Fig.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 material of the first signal electrode 118 and the second signal electrode 119 is copper. In other embodiments, the first signal electrode and the second signal electrode may also be made of other types of metal materials.

[0111] The steps of forming the signal electrode include: Fig.14 As shown, from the side of the piezoelectric stack 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 groove 116 and a second groove 117 exposing the second electrode 106, and the first groove 116 and the second groove 117 are spaced apart; Fig.15 As shown, a signal electrode is formed on the first groove 116 , the second groove 117 , and a portion of the first electrode 104 layer close to the first groove 116 and the second groove 117 .

[0112] In this embodiment, the first electrode 104 and the piezoelectric layer 105 are etched by a dry etching process to expose the second electrode 106 and form the first groove 116 and the second groove 117. The dry etching process has anisotropic etching characteristics and good etching profile controllability, which is conducive to making the morphology of the first groove 116 and the second groove 117 meet the process requirements, and in the process of using the dry etching process, the second electrode 106 and the top of 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 step of forming the first groove 116 and the second groove 117, the piezoelectric stack structure 102 on the top of the first support layer 111 in the peripheral area II is also etched to form a peripheral groove 201 surrounding the working area I, and the peripheral groove 201 exposes the first support layer 111. Compared with the first groove 116 and the second groove 117, the peripheral groove 201 is farther away from the working area I. The peripheral groove 201 provides a spatial position for the subsequent formation of a second support layer surrounding the piezoelectric stack structure 102.

[0115] Continue to refer Fig.15 The filter forming method further includes: after forming the first groove 116 and the second groove 117, before forming the signal electrode, etching the first electrode 104 in a partial area close to the signal electrode to form a top air trench (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 to reflect the sound waves laterally, thereby increasing the residence time of the sound waves in the second cavity formed subsequently, thereby reducing the energy dissipation, which is correspondingly beneficial to improving the acoustic-to-electric conversion performance of the resonator. In this embodiment, the top air groove 126 and the bottom air groove 125 jointly define the effective resonance area. In addition, it should be noted that only after the top air groove 126 is formed can the range of the working vibration frequency of the resonator be tested, which is used as a reference for the subsequent frequency modulation of the first electrode 104 of a partial thickness in the etching working area I.

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

[0118] It should be noted that both the first signal electrode 118 and the second signal electrode 119 have partial areas located on the first electrode 104, and the corresponding first signal electrode 118 and the second signal electrode 119 are electrically connected to the first electrode 104. Because 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 makes the part of the first electrode 104 disconnected by the top air groove 126 and the second electrode 106 at the same potential. When the resonator is working, the induced potential generated by the first electrode 104 on the side of the top air groove 126 away from the working area I is reduced, which is beneficial to reducing the influence of parasitic effects; similarly, the second signal electrode 119 makes the part of the second electrode 106 disconnected by the bottom air groove 125 and the first electrode 104 at the same potential. When the resonator is working, the induced potential generated by the second electrode 106 on the side of the bottom air groove 125 away from the working area I is reduced, which is beneficial to reducing the influence of parasitic effects.

[0119] like Fig.16 As shown, the method for forming the filter further includes: after forming the passivation layer 114 , forming a second cavity 120 on a 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 respectively located on both sides of the piezoelectric stack structure 102. When the resonator is working, the first cavity and the second cavity 120 play the role of coupling, vibration amplification and tuning performance control.

[0121] Specifically, the step of forming the 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 groove 201 .

[0122] The second substrate 122 may be any suitable base material known to those skilled in the art, for example, at least one of the following materials: silicon, germanium, silicon germanium, 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. Fig.16 , showing a schematic structural diagram of the filter of the present invention.

[0124] The filter includes: a piezoelectric stacked structure 102, wherein the piezoelectric stacked structure 102 includes a piezoelectric layer 105, including a first side 1051 and a second side 1052 opposite to the first side 1051, and the piezoelectric stacked structure 102 also includes a first electrode 104 located on the first side 1051 and a second electrode 106 located on the second side 1052; the piezoelectric stacked structure 102 includes a plurality of resonance zones distributed on a plane, wherein the resonance zones are used to form a resonator, wherein the plurality of resonance zones include a target resonance zone for forming a resonator with the highest vibration frequency; a passivation layer 114, which is located on the first electrode 104, wherein the thickness of the passivation layer 114 in the target resonance zone is less than the thickness of the passivation layer 114 in the other resonance zones.

[0125] The resonator provided by the present invention includes a piezoelectric stacked structure 102, in which the thickness of the passivation layer 114 in the target resonance area is less than the thickness of the passivation layer 114 in other resonance areas. Because the thinner the thickness of the passivation layer 114 is, the higher the vibration frequency is, so the vibration frequency of the passivation layer 114 in the target resonance area is faster than the vibration frequency of the passivation layer 114 in other resonance areas, and the frequency of the resonator in the target resonance area is shifted to the right (that is, the high frequency value increases), which is conducive to using the target resonance area to form a resonator with the highest vibration frequency. The corresponding filter bandwidth is manifested as an increase in the bandwidth of the filter, because the first thinning treatment further reduces the surface roughness of the passivation layer 114 in the target resonance area, which means that the thickness uniformity of the passivation layer 114 in the target resonance area is improved, so that the frequency on the right side of the filter bandwidth (high frequency value) is modulated, which improves the uniformity of the frequency on the right side of the filter bandwidth. When measuring, more frequency points will fall within the range required by the specification, which is conducive to improving the yield of the filter.

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

[0127] In this embodiment, the filter includes three resonators, and the corresponding piezoelectric stacked structure 102 includes three resonance zones, which are low resonance zone, middle resonance zone and high resonance zone according to the vibration frequency of the resonator, and the target resonance zone is the high resonator.

[0128] It should be noted that the resonance area includes a working area I and a peripheral area II surrounding the working area I. The working area I of the resonator refers to the area that can store and release energy. It is composed of energy storage elements (such as capacitors and inductors). The main function of the working area I is to maintain oscillation, that is, to store and transfer energy so that the resonator can maintain the stability of amplitude and frequency. The peripheral area II of the resonator refers to other circuits or components connected to the resonator. The function of the peripheral area 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, and 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 the electrical signal and the acoustic signal, so that the filter can filter the signal.

[0131] In this embodiment, the first electrode 104 serves as the upper electrode of the piezoelectric stack structure 102. The material of the first electrode 104 is a conductive material. The conductive material may be a metal material having conductive properties, for example, one or more of Mo, Al, Cu, Pt, Au, Ir, Os, Re, Pd, Rh, Ru, Mo and W.

[0132] The material of the piezoelectric layer 105 is piezoelectric material, which is a crystalline material that will generate voltage between the two end surfaces when subjected to pressure. The piezoelectric material has a piezoelectric effect. The piezoelectric effect of the piezoelectric material can be used to realize the mutual conversion between mechanical vibration (sound waves) and alternating current, thereby realizing the conversion of sound energy into electrical energy.

[0133] In this embodiment, the second electrode 106 serves as the upper electrode of the piezoelectric stack structure 102. The material of the second electrode 106 is a conductive material. The conductive material may be a metal material having conductive properties, for example, one or more of Mo, Al, Cu, Pt, Au, Ir, Os, Re, Pd, Rh, Ru, Mo and W.

[0134] The filter further comprises: a mass load layer 101 located on the second electrode 106 at the second side 1052 .

[0135] The mass load layer 101 is used to effectively reflect the transverse mode to the working area I, effectively suppressing the transverse leakage of energy, so as to achieve the purpose of improving the Q value.

[0136] In this embodiment, the mass loading layer 101 is in a continuous ring shape or a discontinuous ring shape.

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

[0138] In this embodiment, the thickness of the mass load layer 101 in the working area I in each of the resonance zones is different, which is determined by the design frequency of the resonator in each resonance zone. Specifically, the thickness of the mass load layer 101 in the high resonance zone is the thinnest, followed by the mass load layer 101 in the middle resonance zone, and the thickness of the mass load layer 101 in the low resonance zone is the thickest. Correspondingly, the thickness of the mass load layer 101 in the target resonance zone is the smallest. The vibration frequencies of mass load layers 101 of different thicknesses are different. Specifically, the thicker the mass load layer 101, the lower the resonant frequency of the resonator, and the thinner the mass load layer 101, the larger the resonant frequency of the resonator. The resonators formed by the high resonance zone, the middle resonance zone and the low resonance zone have different resonant frequency regions, which realizes the selection of specific frequencies. These resonators with different vibration frequencies constitute the frequency response range of the filter, that is, the bandwidth.

[0139] It should be noted that the thickness of the mass load layer 101 in the working area I is less than that in the peripheral area II. The resonator selects a specific frequency and generates a stable oscillation signal, which is related to the thickness of the mass load layer 101 in the working area I, and has nothing to do with the thickness of the mass load layer 101 in the peripheral area II. The mass load layer 101 in the working area I is formed by thinning, and is therefore thinner than the mass load layer 101 in the peripheral area II.

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

[0141] The bottom air groove 125 is used to reflect the sound waves laterally, which is beneficial to increase the residence time of the sound waves in the cavity, thereby reducing the dissipation of energy, which is correspondingly beneficial to improving the acoustic-to-electric conversion performance of the resonator. The top air groove 126 is used to reflect the sound waves laterally, thereby increasing the residence time of the sound waves in the second cavity 120, thereby reducing the dissipation of energy, which is correspondingly beneficial to improving the acoustic-to-electric conversion performance of the resonator. In this embodiment, the top air groove 126 and the bottom air groove 125 jointly define the effective resonance area.

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

[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 material of the edge protrusion structure and the second electrode is the same, 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 integrated structure.

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

[0145] The first cavity 115 is beneficial to reducing the vibration energy loss of the resonator and can improve the acoustic-to-electric conversion performance of the resonator.

[0146] In this embodiment, the material of the passivation layer 114 and the material of the mass load layer 101 have different frequency changes, that is, different frequency response characteristics. The ratio of the frequency response coefficients of the mass load layer 101 and the passivation layer 114 with the same thickness is 4 to 6.66.

[0147] As an example, the frequency response of the mass load layer 101 with a thickness of 1 nm is 1.8 MHz to 2.2 MHz. The frequency response of the passivation layer 114 with a thickness of 1 nm is 0.3 MHz to 0.5 MHz. Specifically, the material of the passivation layer 114 is silicon nitride.

[0148] It should be noted that the passivation layer 114 of the target resonance area should not be too thick or too thin. If the passivation layer 114 of the target resonance area is too thin, the passivation layer 114 cannot protect the first electrode 104 well, resulting in reduced reliability of the resonator. If the passivation layer 114 of the target resonance area is too thick, the frequency improvement of the high frequency band of the bandwidth of the filter is not significant, resulting in poor uniformity on the right side of the filter and poor yield of the filter. In this embodiment, the thickness of the passivation layer 114 of the target resonance area is 200 angstroms to 600 angstroms.

[0149] It should be noted that the thickness difference between the passivation layer 114 of the target resonance zone and the passivation layer 114 of other resonance zones should not be too large or too small. If the thickness difference is too large, the passivation layer 114 of the corresponding target resonance zone is too thin, and the passivation layer 114 cannot protect the first electrode 104 well, resulting in reduced reliability of the resonator. If the thickness difference is too small, the passivation layer 114 of the corresponding target resonance zone is too thick, resulting in an insignificant frequency increase in the high-frequency band of the bandwidth of the filter, resulting in 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 resonance zone and the passivation layer 114 of other resonance zones is 20 angstroms to 40 angstroms.

[0150] It should also be noted that the thickness of the passivation layer 114 in the working area I of the target resonance area is less than the thickness of the passivation layer 114 in the peripheral area II of the target resonance area, and the thickness of the passivation layer 114 in the peripheral area II of the target resonance area is the same as the thickness of the passivation layer 114 in other resonance areas. When working, the working area 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 area II is not helpful for the working area I to generate clock signals of various predetermined frequencies.

[0151] The resonator further includes: a signal electrode, which runs through the first electrode 104 and the piezoelectric layer 105 of the peripheral region II from one side of the first electrode 104, the bottom of the signal electrode is located on the second electrode 106, and the signal electrode is spaced apart from the second supporting layer 121. Specifically, the signal electrode includes a first signal electrode 118 and a second signal electrode 119, and 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.

[0152] The signal electrode is used to connect the upper electrode and the lower electrode, and its function is to transmit a signal or excite the resonator to generate oscillation or adjust the performance of the resonator.

[0153] In the present embodiment, partial areas of the first signal electrode 118 and the second signal electrode 119 are both located on the first electrode 104, and the corresponding first signal electrode 118 and the second signal electrode 119 are both electrically connected to the first electrode 104. Because 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 makes the portion of the first electrode 104 disconnected by the top air groove 126 and the second electrode 106 at the same potential. When the resonator is working, the induced potential generated by the first electrode 104 on the side of the top air groove 126 away from the working area I is reduced, which is beneficial to reducing the influence of parasitic effects. Similarly, the second signal electrode 119 makes the portion of the second electrode 106 disconnected by the bottom air groove 125 and the first electrode 104 at the same potential. When the resonator is working, the induced potential generated by the second electrode 106 on the side of the bottom air groove 125 away from the working area I is reduced, which is beneficial to reducing the influence of parasitic effects.

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

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

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

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

[0158] The filter of the embodiment of the present invention may be formed by the method for forming the filter of the aforementioned embodiment, or may be formed by other methods for forming filters, which will not be described in detail in this embodiment.

[0159] Correspondingly, an embodiment of the present invention further provides an electronic device, and the electronic device includes the filter of the above embodiment.

[0160] The filter can be assembled into various electronic devices. As can be seen from the above analysis, the reliability of the filter is high, which can correspondingly obtain electronic devices with high reliability. Among them, the electronic devices can also be personal computers, mobile terminals such as smart phones, media players, navigation devices, electronic game devices, game controllers, tablet computers, wearable devices, anti-access electronic systems, POS terminals, medical equipment, flight simulators, etc.

[0161] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A method for forming a filter, characterized in that: include: A piezoelectric stack structure is provided, the piezoelectric stack structure comprising a piezoelectric layer, the piezoelectric layer comprising 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 comprises a plurality of resonance regions distributed on a plane, the resonance regions are used to form a resonator, and the plurality of resonance regions include a target resonance region for forming a resonator with the highest vibration frequency; forming a passivation material layer covering the first electrode on the first side; A first thinning process is performed on the passivation material layer of the target resonance region to form a passivation layer.

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

3. The method for forming a filter according to claim 1, wherein: In the step of forming a passivation layer, the thickness of the passivation layer in the target resonance region is 200 angstroms to 600 angstroms.

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

5. The method for forming a filter according to claim 1, wherein: The first thinning step includes: performing initial thinning on the passivation material layer of the target resonance region; Performing thickness detection on the passivation material layer after initial thinning to obtain the thickness of the passivation material layer that needs to be further thinned; The passivation material layer is thinned again according to the thickness that needs to be further thinned to form the passivation layer.

6. The method for forming a filter according to claim 1, wherein: The resonance region includes a working region and a peripheral region surrounding the working region; During the first thinning process, the passivation material layer in the working area of ​​the target resonance area is thinned.

7. The method for forming a filter according to claim 1, wherein: The step of forming a 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; The passivation material film is subjected to a second thinning process to form the passivation material layer.

8. The method for forming a filter according to claim 1, wherein: The resonance region includes a working region and a peripheral region surrounding the working region; The filter forming method further includes: forming a mass load layer on the second electrode from the second side, and the thickness of the mass load layer in the working area of ​​each of the resonance areas is different.

9. The method for forming a filter according to claim 8, wherein: The filter forming method further includes: providing an expected thickness of the mass load layer in the working region in the target resonance region; The step of forming a mass load layer on the second electrode from the second side includes: a thickness of the mass load layer in an operating region in the target resonance region is greater than the expected thickness.

10. The method for forming a filter according to claim 8, wherein: A ratio of the frequency change rate of the mass load layer to that of the passivation layer is 4 to 6.

66.

11. The method for forming a filter according to claim 9, wherein: The difference between the thickness of the mass loading layer in the working region in the target resonance region and the expected thickness is 20 angstroms to 40 angstroms.

12. The method for forming a filter according to claim 8, wherein: The step of forming a mass loading layer on the second electrode from the second side comprises: forming a mass loading material layer on the second electrode from the second side; The mass load material layer in the working area in each of the resonance areas is thinned to different thicknesses to form the mass load layer.

13. The method for forming a filter according to claim 1, wherein: The filter forming method further includes: before forming the passivation material layer, forming a first cavity on a side of the second electrode away from the piezoelectric layer; After the passivation layer is formed, a second cavity is formed on a side of the first electrode away from the piezoelectric layer.

14. The method for forming a filter according to claim 1, wherein: The material of the passivation layer includes silicon nitride.

15. A filter, characterized in that: include: A piezoelectric stack structure, the piezoelectric stack structure comprising a piezoelectric layer, comprising 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 comprising a plurality of resonance regions distributed on a plane, the resonance regions being used to form a resonator, the plurality of resonance regions including a target resonance region for forming a resonator with a highest vibration frequency; A passivation layer is located on the first electrode, and the thickness of the passivation layer in the target resonance area is smaller than the thickness of the passivation layer in other resonance areas.

16. The filter according to claim 15, characterized in that The thickness of the passivation layer in the target resonance region is 200 angstroms to 600 angstroms.

17. The filter according to claim 15, characterized in that The thickness difference between the passivation layer of the target resonance region and the passivation layers of the other resonance regions is 20 angstroms to 40 angstroms.

18. The filter according to claim 15, characterized in that The material of the passivation layer includes silicon nitride.

19. The filter according to claim 15, characterized in that The filter further includes: a mass loading layer located on the second electrode at the second side.

20. The filter according to claim 19, characterized in that The thickness of the mass load layer in the working area of ​​each of the resonance regions is different.

21. The filter according to claim 19, characterized in that The ratio of the frequency response coefficients of the mass-loading layer with the same thickness and the passivation layer with the same thickness is 4 to 6.

66.

22. The filter according to claim 15, characterized in that The filter further comprises: A first cavity is located at a side of the second electrode away from the piezoelectric layer; The second cavity is located at a side of the first electrode away from the piezoelectric layer.

23. An electronic device, characterized in that: Comprising a filter as claimed in any one of claims 15 to 22.

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