Resonator and method of forming the same, electronic device

Abstract

The application discloses a resonator and a forming method thereof, and an electronic device. The resonator comprises a substrate, an acoustic mirror, a bottom electrode, a piezoelectric layer, a top electrode, a patterned load layer, and a passivation layer. In the patterned load layer, the proportion of the load material coverage area to the total effective area of the resonator is defined as a pattern duty cycle, which is denoted as r and satisfies 0≤r≤1. The resonator satisfies the following limited condition: (Fs1-Fs2) / Fs1≤K, wherein Fs1 is the series resonance frequency of the resonator without the load layer, Fs2 is the series resonance frequency of the resonator with the load layer with r=1, and K is a preset threshold. The thickness of the load layer is controlled so that the resonator satisfies the limited condition of (Fs1-Fs2) / Fs1≤K. At this time, the use of the patterned load layer basically has no impact on the performance of the resonator and does not have obvious deterioration, thereby improving the device yield. The technical scheme of the application has the advantages of simplicity and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microelectronics, in particular to a resonator and a forming method thereof, and an electronic device. BACKGROUND

[0002] In recent years, the acceleration of the miniaturization and high performance trend of communication equipment has brought higher challenges to the radio frequency front end. In a typical structure of an ordinary filter, there are inductors and a plurality of resonators (usually referred to as series resonators) between the input end and the output end, a plurality of branches (usually referred to as parallel branches) between the connection points of each series resonator and the ground end, and resonators (usually referred to as parallel resonators) and inductors arranged on each parallel branch. A mass load layer is added to each parallel resonator, so that the frequency of the parallel resonator and the frequency of the series resonator have a difference to form the passband of the filter.

[0003] By graphically designing the load layer, the frequency freedom of each resonator in the filter design can be increased, thereby improving the performance of the filter. However, experiments show that a too thick load layer will greatly affect the performance of the filter. SUMMARY

[0004] Therefore, the present application provides a resonator capable of flexibly adjusting the frequency freedom of the resonator, a manufacturing method thereof, and an electronic device comprising the resonator.

[0005] The first aspect of the present application provides a resonator, comprising: a substrate, an acoustic mirror, a bottom electrode, a piezoelectric layer, a top electrode, a graphically designed load layer, and further comprising a passivation layer, wherein in the graphically designed load layer, the pattern duty cycle is the ratio of the load material coverage area to the total effective area of the resonator, the pattern duty cycle is r, and 0≤r≤1, and the resonator satisfies the following defined condition: (Fs1-Fs2) / Fs1≤K, wherein Fs1 is the series resonant frequency of the resonator without the load layer, Fs2 is the series resonant frequency of the resonator with the load layer with r=1, and K is a preset threshold value.

[0006] Optionally, the load layer is located below the bottom electrode, below the piezoelectric layer, below the top electrode, below the passivation layer, above the passivation layer, or inside each film layer.

[0007] Optionally, the thickness of the load layer makes the resonator satisfy the defined condition.

[0008] Optionally, the value of K is 1.5%.

[0009] Optionally, the value of K is 1%.

[0010] Optionally, the value of K is 0.8%.

[0011] Optionally, the patterned load layer comprises a plurality of uniform distributed load islands with the same shape and the same size.

[0012] Optionally, the shape of the load island is a regular polygon or a circle.

[0013] Optionally, the plurality of load islands are arranged in a plane periodically.

[0014] Optionally, the patterned load layer comprises a plurality of concentric circular rings or a plurality of concentric polygonal rings.

[0015] Optionally, the patterned load layer is an irregular pattern.

[0016] The second aspect of the present application provides a method for forming a resonator, comprising: forming an acoustic mirror structure on a substrate; forming a bottom electrode on the acoustic mirror structure; forming a piezoelectric layer on the bottom electrode; forming a top electrode on the piezoelectric layer; and further forming a passivation layer on the top electrode; and further comprising: forming a patterned load layer in the resonator, wherein the patterned load layer has a pattern duty cycle, the pattern duty cycle being a ratio of a load material coverage area to a total effective area of the resonator, the pattern duty cycle being r, 0≤r≤1, and the resonator satisfies a defined condition: (Fs1-Fs2) / Fs1≤K, wherein Fs1 is a series resonant frequency of the resonator without the load layer, Fs2 is a series resonant frequency of the resonator with the load layer with r=1, and K is a preset threshold. The above does not limit the forming order of the layers of the resonator, which can be adjusted according to actual conditions, and all belong to the method for forming the resonator.

[0017] Optionally, the patterned load layer is formed before the bottom electrode; or the patterned load layer is formed before the piezoelectric layer; or the patterned load layer is formed before the top electrode; or the patterned load layer is formed before the passivation layer; or the patterned load layer is formed after the passivation layer; or the patterned load layer is formed in the process of forming each film layer.

[0018] Optionally, the thickness of the load layer is controlled to make the resonator satisfy the defined condition.

[0019] Optionally, the value of K is 1.5%.

[0020] Optionally, the value of K is 1%.

[0021] Optionally, the value of K is 0.8%.

[0022] The third aspect of the present application provides an electronic device, characterized in that, comprising any one of the resonators provided by the present application.

[0023] According to the technical solution of the present application, by controlling the thickness of the load layer, the resonator satisfies the limited condition of "(Fs1-Fs2) / Fs1≤K". When the limited condition is satisfied, the use of the patterned load layer basically has no impact on the performance of the resonator, and there is no obvious deterioration, which improves the device yield. The technical solution of the present application has the advantages of being simple and easy to implement. BRIEF DESCRIPTION OF DRAWINGS

[0024] For the purpose of illustration and not limitation, the present application will now be described according to the preferred embodiments of the present application, in particular with reference to the accompanying drawings, in which:

[0025] Figure 1 A cross-sectional view of a resonator with a patterned load layer according to an embodiment of the present application.

[0026] Figures 2a to 2d A comparison chart of Smith charts of different resonators;

[0027] Figure 3 A schematic diagram of the relationship between (Fs1-Fs2) / Fs1 and Rp value;

[0028] Figure 4 A top view schematic diagram of a first patterned load layer in a resonator according to an embodiment of the present application;

[0029] Figure 5 A top view schematic diagram of a second patterned load layer in a resonator according to an embodiment of the present application;

[0030] Figure 6 A top view schematic diagram of a third patterned load layer in a resonator according to an embodiment of the present application;

[0031] Figure 7 A top view schematic diagram of a fourth patterned load layer in a resonator according to an embodiment of the present application;

[0032] Figures 8a to 8g A process schematic diagram of a forming method of a resonator according to an embodiment of the present application. DETAILED DESCRIPTION

[0033] As Figure 1As shown, the resonator of the embodiment of the present application can include, from bottom to top, a substrate 10, an acoustic mirror 20, a bottom electrode 30, a piezoelectric layer 40, a top electrode 50, a patterned load layer 60, and a passivation layer 70. The following description mainly takes the case with the passivation layer 70 as an example. In addition, the resonator can also include an air gap 80 and the like. Among them, in the patterned load layer, the proportion of the load material coverage area to the total effective area of the resonator is defined as the pattern duty cycle, denoted as r and 0≤r≤1. Under the premise that other conditions remain unchanged, the greater the pattern duty cycle r of the load layer, the more obvious the change of the series resonance frequency Fs of the resonator. The resonator of the embodiment of the present application satisfies the following condition: (Fs1-Fs2) / Fs1≤K, wherein Fs1 is the series resonance frequency of the resonator without the load layer (i.e. r=0), Fs2 is the series resonance frequency of the resonator with the load layer with r=1, and K is a preset threshold. Optionally, K can continuously take a value between 0.8% and 1.5%, and preferably K=0.8%.

[0034] Although Figure 1 In the embodiment shown, the patterned load layer 60 is arranged below the passivation layer, but this is only an example and not a limitation. In other embodiments, the load layer 60 can also be flexibly arranged below the bottom electrode 30, below the piezoelectric layer 40, below the top electrode 50, above the passivation layer 70, or inside each film layer.

[0035] By patterned design of the load layer, the frequency freedom of each resonator in the filter design can be increased, thereby improving the performance of the filter. That is, by changing the proportion of the load material coverage area to the total effective area of the resonator (denoted as the pattern duty cycle r) of different resonators in a FBAR filter, the frequency of each resonator can be freely adjusted, and this method helps to simplify the preparation process of the resonator and thus save costs. For example, in a filter composed of n resonators, if m (m≤n) resonators with different frequencies need to be prepared using the process of the prior art, m times of photolithography are required, and the preparation cost is high. After using the point ML process, by setting different pattern duty cycles on the load layers of different resonators, different frequencies of different resonators can be realized through one thin film deposition and photolithography process, thereby simplifying the process flow of preparation and reducing the preparation cost of the FBAR filter chip.

[0036] After the patterned load layer is applied to the resonator, the vibration state of this area and the main vibration state are different, which will have a certain impact on the vibration of the resonator in addition to adjusting the frequency of the resonator. One major aspect is that more secondary resonances will be generated near Fs, which will cause fluctuations in the passband of the filter and affect the normal operation of the filter. Therefore, it is necessary to find the relationship between the point ML and the secondary resonator.

[0037] It is verified that it is difficult to achieve a large frequency difference range with the patterned load layer, and certain limited conditions need to be met to not affect the performance of the resonator. The resonator in the embodiment of the present application proposes a limited condition of "(Fs1-Fs2) / Fs1≤K". Since there is an upper limit to the maximum frequency difference achieved by the patterned load layer when the limited condition is met, the use of the patterned load layer will not basically affect the performance of the resonator; and when the condition is not met, the performance of the resonator will be significantly deteriorated.

[0038] The deterioration of the sub-resonance of the resonator is mainly observed and characterized by the Smith chart. The Smith chart is a polar coordinate diagram representing the reflection coefficient, and the reflection coefficient refers to the ratio of the reflected wave voltage to the incident wave voltage of a single port, which is generally represented as S11. The size of the sub-resonance of the resonator can be judged by observing the Smith chart. The following takes Figure 2a as an example to illustrate the relationship between the Smith chart and the sub-resonance of the resonator. The irregular circle inside the figure represents the performance impedance diagram of the actual resonator, and the two intersection points of the horizontal line in the figure represent Fs and Fp, respectively, and the intersection point on the left represents Fs and the intersection point on the right represents Fp. And the irregular small circles below Fs represent the sub-resonance below Fs. The smaller the small circles and the closer to the Smith circle, the smaller the sub-resonance of the resonator and the better the performance; the larger the small circles and the farther from the Smith circle, the larger the sub-resonance of the resonator and the worse the performance.

[0039] Therefore, in the embodiment of the present application, the performance of the resonator under different K values is analyzed by the Smith chart.

[0040] Figures 2a to 2d The following are the Smith charts of different resonators. The four resonators corresponding to the four Smith charts all use patterned load layer design, and the structures are completely the same except for the thickness of the patterned load layer.

[0041] Figure 2a The corresponding resonator uses a structure without a load layer, and the thickness of the load layer d1=0, i.e. the duty cycle r=0. The shape of the Smith chart is shown in the figure. At this time, the small circles below Fs in the Smith chart are small, and the distance between the small circles and the outer circle is also small, indicating that the sub-resonance of the resonator is small at this time, and this case also represents the baseline value of the performance of the resonator, indicating the normal performance of the resonator.

[0042] Figure 2b The corresponding resonator is provided with a patterned load layer, and the pattern duty cycle is 0 Figure 2bThe smaller circles below Fs are smaller, and their distance from the outer circle is... Figure 2a The difference between the two is not significant, indicating that the secondary resonance of the resonator is small under this point-like ML condition, and the resonator performance does not degrade significantly. The patterned load layer that meets the constraints has basically no impact on the resonator performance.

[0043] Figure 2c The corresponding resonator incorporates a patterned load layer with a duty cycle of 0 < r < 1. By controlling the thickness of the load layer to d3 (d3 > d2), (Fs1 - Fs2) / Fs1 = 2.4%. As shown in the figure, Figure 2c The small circles below Fs are significantly larger, and the distance between this region and the outer Smith circle increases, indicating that the resonator performance has degraded and the secondary resonance of the resonator has been significantly enhanced.

[0044] Figure 2d The corresponding resonator incorporates a patterned load layer with a duty cycle of 0 < d2 / d1 < 1. By controlling the load layer thickness to d4 (d4 > d3), (Fs1 - Fs2) / Fs1 = 4%. As shown in the figure, the circles below Fs in Figure 2D are larger and farther from the Smith circle, indicating resonator performance degradation. The secondary resonance of the resonator is significantly enhanced, and the degree of degradation is greater than [missing information]. Figure 2c Corresponding implementation examples.

[0045] Depend on Figures 2a to 2d A comparison of the four figures shows that as (Fs1-Fs2) / Fs1 increases, that is, as the thickness of the load layer increases, the performance deteriorates significantly, and the secondary resonance of the resonator gradually strengthens. Therefore, a patterned load layer process needs to be used within a certain thickness range.

[0046] Figure 3 The graph shows the curve of (Fs1-Fs2) / Fs1 versus the parallel resonant frequency, illustrating the trend of Rp as a function of (Fs1-Fs2) / Fs1. In practical filter design, Rp needs to be as large as possible to achieve better performance; therefore, it is undesirable for the introduction of point-like ML technology to reduce Rp. Figure 3As shown in the table, when the value of (Fs1-Fs2) / Fs1 is greater than 0.8%, Rp also has a certain decrease; as (Fs1-Fs2) / Fs1 increases to 1%, the degree of deterioration gradually becomes serious; when the value of (Fs1-Fs2) / Fs1 is greater than 1.5%, the performance degradation exceeds 10%, which has obviously exceeded the conventional process fluctuation range. In other words, as the thickness of the patterned load layer increases, the sub-resonance of the resonator gradually becomes serious. When (Fs1-Fs2) / Fs1≤1.5%, especially when (Fs1-Fs2) / Fs1≤0.8%, the value of Rp is basically unchanged. Therefore, the thickness of the load layer can be controlled to make the resonator meet the defined condition of (Fs1-Fs2) / Fs1≤1.5%, or preferably meet the defined condition of (Fs1-Fs2) / Fs1≤1%, or more preferably meet the defined condition of (Fs1-Fs2) / Fs1≤0.8%. When the defined condition is met, the use of the patterned load layer basically has no effect on the sub-resonance of the resonator, and the performance deterioration can be avoided, thereby improving the device yield.

[0047] Therefore, by the above Figures 2a to 2d and Figure 3 It can be known that the thickness of the load layer needs to be controlled to make the resonator meet the defined condition of (Fs1-Fs2) / Fs1≤1.5%; or preferably meet the defined condition of (Fs1-Fs2) / Fs1≤1%; or more preferably meet the defined condition of (Fs1-Fs2) / Fs1≤0.8%. When the defined condition is met, the use of the patterned load layer basically has no effect on the sub-resonance of the resonator, and the performance deterioration can be avoided, thereby improving the device yield.

[0048] In the resonator of the embodiment of the present application, the patterned load layer can include a plurality of uniformly distributed load islands with the same shape and the same size. The shape of the load island is a regular polygon or a circle, etc. The plurality of load islands can be arranged in a planar periodic manner, etc. The embodiments are listed as shown in Figure 4 and Figure 5 The above is only an example of the shape of the load island, but the shape of the load island is not limited thereto.

[0049] Figure 4 In the embodiment shown in the table, the regular pentagonal outer frame represents the effective area of the resonator, and the plurality of square load islands arranged in a regular square lattice manner represent a plurality of load islands. The distance between the center points of two adjacent square load islands is d1, and the side length of a single square load island is d2. The duty cycle r=(d2 / d1) can be adjusted by adjusting the ratio of d2 / d1, and finally the frequency of the resonator is adjusted. 2 .

[0050] Figure 5 In the embodiment shown in the table, the regular pentagonal outer frame represents the effective area of the resonator, and the plurality of circular dots arranged in a planar close-packed triangular manner represent a plurality of load islands. In the case where the distance between the circular dots is a fixed value, the larger the diameter, the larger the duty cycle; or in the case where the diameter of the circular dot is a fixed value, the larger the distance, the smaller the duty cycle. Therefore, the duty cycle can be adjusted by adjusting the diameter and distance of the circular dot, and finally the frequency of the resonator is adjusted.

[0051] In the resonator of the embodiment of the present application, the patterned load layer can include a plurality of concentric circular rings or a plurality of concentric polygonal ring-shaped load rings. The embodiments are shown in Figs. 1 and 2. Figure 6 and Figure 7

[0052] Figure 6 In the embodiment shown in Fig. 3, the circular outer frame represents the effective area of the resonator, and the plurality of shaded concentric circular rings represent the plurality of load rings. In the case where the spacing of the circular rings is a fixed value, the greater the width of the circular ring, the greater the duty cycle; or in the case where the width of the circular ring is a fixed value, the greater the spacing of the circular ring, the smaller the duty cycle. Therefore, the duty cycle can be adjusted by adjusting the width and spacing of the circular ring, and finally the frequency of the resonator is adjusted.

[0053] Figure 7 In the embodiment shown in Fig. 4, the regular pentagonal outer frame represents the effective area of the resonator, and the plurality of shaded concentric pentagonal ring-shaped rings represent the plurality of load rings. In the case where the spacing of the pentagonal ring is a fixed value, the greater the width of the pentagonal ring, the greater the duty cycle; or in the case where the width of the pentagonal ring is a fixed value, the greater the spacing of the pentagonal ring, the smaller the duty cycle. Therefore, the duty cycle can be adjusted by adjusting the width and spacing of the pentagonal ring, and finally the frequency of the resonator is adjusted.

[0054] In addition, the patterned load layer can also be a non-periodic irregular pattern.

[0055] For those skilled in the art to better understand the embodiments of the present application, reference is made to Figures 8a to 8g , which describes in detail the forming method of the resonator of the embodiments of the present application.

[0056] Details of the structure in the figure are described:

[0057] 10: substrate, optional materials are single crystal silicon, gallium arsenide, sapphire, quartz, silicon carbide, etc.

[0058] 20: acoustic mirror, which can be a cavity, or a Bragg reflection layer and other equivalent forms, which are taken as an example in the case of a cavity here and in the figure to illustrate the embodiment;

[0059] 21: acoustic mirror filling material, which can be SiO, SiN and other dielectric materials and doped materials thereof;

[0060] 30: bottom electrode (electrode pin), the material can be selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or alloys thereof or alloys thereof;

[0061] 40: piezoelectric layer, which can be selected from aluminum nitride, zinc oxide, PZT and other materials and rare earth element doped materials containing a certain atomic ratio of the above materials; ​

[0062] 50: top electrode (electrode pin), material Mo or alloy thereof, etc.

[0063] 60: load layer, material Mo, Ru, Au, Al, Mg, W, Cu, Ti, Ir, Os, Cr or alloy thereof, etc., AlN, ZnO, PZT, etc., and rare earth element doped material containing a certain atomic ratio of the above materials;

[0064] 70: passivation layer, AlN, SiN, SiO2, etc.

[0065] 80: air gap;

[0066] 82: air gap filling material, SiO, SiN, etc., dielectric material and its doped material.

[0067] As shown in Figure 8a , the acoustic mirror filling structure 21 is prepared on the top of the substrate 10. Specifically, the substrate 10 of single crystal silicon material is provided, photoresist is coated on the top, a groove is made on the top surface of the substrate 10 by using photolithography and etching technology, then the sacrificial material SiO is deposited, and the structure is polished flat by chemical mechanical polishing to form Figure 8a structure.

[0068] As shown in Figure 8b , the bottom electrode 30 is prepared. Specifically, the metal molybdenum is deposited as the electrode material, and then the patterned bottom electrode 30 is made by using photolithography and etching technology.

[0069] As shown in Figure 8c , the piezoelectric layer 40 is deposited. Specifically, the aluminum nitride material is deposited to form the piezoelectric layer 40.

[0070] As shown in Figure 8d , the air gap filling material 82 is prepared. Specifically, the silicon oxide material is deposited on the piezoelectric layer 40, and a patterned mask is made on the silicon oxide. The mask material can be photoresist or hard mask layer; then the unmasked area is etched to remove the silicon oxide; and then the mask is removed to obtain the patterned air gap filling material 82.

[0071] As shown in Figure 8e , the top electrode 50 is prepared. Specifically, the metal molybdenum is deposited as the electrode material, and then the patterned top electrode 50 is made by using photolithography and etching technology.

[0072] As shown in Figure 8f , the patterned load layer 60 is prepared. Specifically, a patterned mask is made on the top electrode 50. The mask material can be negative photoresist; then molybdenum is deposited as the load layer material in the hollow part of the mask; and then the Lift-off process is performed to remove the photoresist and the load layer material on the photoresist, thereby obtaining the patterned load layer 60.

[0073] As Figure 8g , the passivation material is deposited to form a passivation layer 70, and the acoustic mirror filling structure 21 and the air gap filling material 82 are removed, to obtain the acoustic mirror 20 and the air gap 80, i.e. to obtain the final resonator.

[0074] It should be noted that the preparation of the air gap 80 is optional and not necessary. Here, only the process flow when the load layer is on the top electrode is exemplified. In other embodiments, the load layer can also be located at any position in the thickness direction of the resonator. Specifically, from the preparation process, the patterned load layer can be formed before the bottom electrode; or, the patterned load layer is formed before the piezoelectric layer; or, the patterned load layer is formed before the top electrode; or, the patterned load layer is formed before the passivation layer; or, the patterned load layer is formed after the passivation layer; or, the patterned load layer is formed in the process of forming each film layer.

[0075] In the method for forming the resonator according to the embodiments of the present application, the thickness of the load layer can be controlled to make the resonator satisfy the defined condition.

[0076] In the method for forming the resonator according to the embodiments of the present application, the value of K can be 1.5%, 1% or 0.8%.

[0077] The electronic device according to the embodiments of the present application, which comprises any one of the resonators disclosed in the present application.

[0078] According to the technical solution of the embodiments of the present application, the thickness of the load layer is controlled to make the resonator satisfy the defined condition of "(Fs1-Fs2) / Fs1≤K". When the defined condition is satisfied, the use of the patterned load layer basically has no impact on the performance of the resonator, and there is no obvious deterioration, which improves the device yield. The technical solution of the embodiments of the present application has the advantages of being simple and easy to implement.

[0079] The specific embodiments described above do not constitute a limitation on the protection scope of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made depending on design requirements and other factors. Any modification, equivalent replacement and improvement made within the spirit and principles of the present application shall fall within the scope of the protection of the present application.

Claims

1. A resonator characterized by, The resonator comprises: a substrate, an acoustic mirror, a bottom electrode, a piezoelectric layer, a top electrode, a patterned load layer, wherein in the patterned load layer, a pattern duty cycle r is 0≤r≤1, the pattern duty cycle is a ratio of a load material coverage area to a total effective area of the resonator, and the resonator satisfies a defined condition as follows: (Fs1-Fs2) / Fs1≤K, wherein Fs1 is a series resonant frequency of the resonator without the load layer, Fs2 is a series resonant frequency of the resonator with the load layer of r=1, and K is a preset threshold value; a thickness of the load layer is controlled to make the resonator satisfy the defined condition.

2. The resonator according to claim 1, wherein: the resonator further has a passivation layer; the load layer is located below the bottom electrode, below the piezoelectric layer, below the top electrode, below the passivation layer, above the passivation layer, or inside the film layers.

3. The resonator of claim 1, wherein the value of K is 1.5%.

4. The resonator of claim 1, wherein the value of K is 1%.

5. The resonator of claim 1, wherein the value of K is 0.8%.

6. The resonator according to any one of claims 1 to 5, characterized in that, the patterned load layer comprises a plurality of uniform distributed load islands with the same shape and size.

7. The resonator of claim 6, wherein the shape of the load islands is a regular polygon or a circle.

8. The resonator of claim 6, wherein, the plurality of load islands are arranged in a planar periodic manner.

9. The resonator of any one of claims 1 to 5, wherein, the patterned load layer comprises a plurality of concentric circular rings or a plurality of concentric polygonal ring-shaped load rings.

10. The resonator of any one of claims 1 to 5, wherein, the patterned load layer is an irregular pattern.

11. A method of forming a resonator, characterized by, The resonator comprises: forming an acoustic mirror structure on a substrate; forming a bottom electrode on the acoustic mirror structure; forming a piezoelectric layer on the bottom electrode; forming a top electrode on the piezoelectric layer; and, further comprising: forming a patterned load layer in the resonator, wherein in the patterned load layer, a pattern duty cycle r is 0≤r≤1, the pattern duty cycle is a ratio of a load material coverage area to a total effective area of the resonator, and the resonator satisfies a defined condition as follows: (Fs1-Fs2) / Fs1≤K, wherein Fs1 is a series resonant frequency of the resonator without the load layer, Fs2 is a series resonant frequency of the resonator with the load layer of r=1, and K is a preset threshold value; a thickness of the load layer is controlled to make the resonator satisfy the defined condition.

12. The method for forming the resonator according to claim 11, wherein: further comprising: forming a passivation layer on the top electrode; the patterned load layer is formed before the bottom electrode; or, the patterned load layer is formed before the piezoelectric layer; or, the patterned load layer is formed before the top electrode; or, the patterned load layer is formed before the passivation layer; or, the patterned load layer is formed after the passivation layer; or, the patterned load layer is formed in a process of forming the film layers.

13. The method of forming a resonator of claim 11, wherein, the value of K is 1.5%.

14. The method of forming a resonator of claim 11, wherein, the value of K is 1%.

15. The method of forming a resonator of claim 11, wherein, the value of K is 0.8%.

16. An electronic device, comprising: The resonator comprises: a substrate, an acoustic mirror, a bottom electrode, a piezoelectric layer, a top electrode, a patterned load layer, wherein in the patterned load layer, a pattern duty cycle r is 0≤r≤1, the pattern duty cycle is a ratio of a load material coverage area to a total effective area of the resonator, and the resonator satisfies a defined condition as follows: (Fs1-Fs2) / Fs1≤K, wherein Fs1 is a series resonant frequency of the resonator without the load layer, Fs2 is a series resonant frequency of the resonator with the load layer of r=1, and K is a preset threshold value; a thickness of the load layer is controlled to make the resonator satisfy the defined condition.

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