Resonator, filter and manufacturing method

Abstract

The embodiment of the present application provides a resonator, a filter and a manufacturing method, wherein the manufacturing method of the resonator comprises the following steps: forming a bottom electrode; forming a piezoelectric layer on the bottom electrode; forming at least one recess on the piezoelectric layer, the depth of the recess is the same as the thickness of a mass load layer to be formed; forming an upper electrode on the piezoelectric layer, the part of the upper electrode filled into the recess forms the mass load layer, and the upper surface of the upper electrode is planarized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor devices, and in particular to a resonator, a filter and a manufacturing method. BACKGROUND

[0002] Resonators are widely used in various electronic products, for example, can be used to generate various predetermined frequency clock signals. A resonator in the prior art is shown in Figure 1, which includes a bottom electrode, a piezoelectric layer and an upper electrode formed on a substrate cavity. In order to enable different resonators to generate different predetermined frequency clock signals, it is necessary to form a mass loading layer of different thickness on the upper electrode. The conventional method is to form a mass loading layer of different thickness on the upper electrode or the bottom electrode by using a Liftoff process, as shown in Figures 2 and 3. A patterned photoresist 12 is formed on the electrode 11, then a metal layer 13 is deposited, and finally the photoresist 12 and the metal layer 13 on the photoresist 12 are removed, leaving only the metal layer 13 deposited on the electrode 11, thereby forming a mass loading layer. Figure 1A and Figure 1B However, this method has the following disadvantages. Firstly, photoresist residues are likely to occur on the electrode during the Liftoff process, causing the mass loading layer to be in poor contact with the upper electrode or the bottom electrode, thereby causing product defects. Secondly, this method affects the quality of the formed mass loading layer when forming a thinner mass loading layer, and is more likely to cause product defects. In addition, this method can only adjust the upper electrode or the bottom electrode, and is not flexible enough for resonant frequency adjustment.

[0003] However, this method has the following disadvantages. Firstly, photoresist residues are likely to occur on the electrode during the Liftoff process, causing the mass loading layer to be in poor contact with the upper electrode or the bottom electrode, thereby causing product defects. Secondly, this method affects the quality of the formed mass loading layer when forming a thinner mass loading layer, and is more likely to cause product defects. In addition, this method can only adjust the upper electrode or the bottom electrode, and is not flexible enough for resonant frequency adjustment. SUMMARY

[0004] Therefore, the embodiments of the present application provide a resonator, a filter and a manufacturing method to solve at least one of the problems of poor contact between the mass loading layer and the upper electrode or the bottom electrode, poor quality of the mass loading layer when forming a thinner mass loading layer, and insufficient flexibility for resonant frequency adjustment in the prior art.

[0005] According to a first aspect, the embodiments of the present application provide a manufacturing method of a resonator, comprising: forming a bottom electrode; forming a piezoelectric layer on the bottom electrode; forming at least one recess on the piezoelectric layer, the depth of the recess being the same as the thickness of a mass loading layer to be formed; forming an upper electrode on the piezoelectric layer, the part of the upper electrode filling into the recess forming the mass loading layer, and the upper surface of the upper electrode being planarized.

[0006] Optionally, before the forming the bottom electrode, further comprising: forming at least one opening on the substrate surface; filling a sacrificial layer into the opening; and after the planarizing the upper surface of the upper electrode, further comprising: removing the sacrificial layer to form a cavity between the bottom electrode and the substrate.

[0007] Optionally, the resonator is multiple, the forming the bottom electrode comprises: forming multiple separated bottom electrodes, each of the bottom electrodes corresponding to one of the resonators; or the forming the bottom electrode comprises: forming an integrated bottom electrode, the multiple resonators sharing the integrated bottom electrode; or the forming the piezoelectric layer on the bottom electrode comprises: forming multiple separated piezoelectric layers, each of the piezoelectric layers corresponding to one of the resonators; or the forming the piezoelectric layer on the bottom electrode comprises: forming an integrated piezoelectric layer, the multiple resonators sharing the integrated piezoelectric layer; or the forming the upper electrode on the piezoelectric layer comprises: forming multiple separated upper electrodes, each of the upper electrodes corresponding to one of the resonators; or the forming the upper electrode on the piezoelectric layer comprises: forming an integrated upper electrode, the multiple resonators sharing the integrated upper electrode.

[0008] Optionally, the forming the at least one recess on the piezoelectric layer comprises: forming a mask layer on the piezoelectric layer; removing part of the mask layer on the piezoelectric layer corresponding to the resonators which need to form the mass load layer to expose part of the surface of the piezoelectric layer where the recess is to be formed; etching the exposed part of the surface of the piezoelectric layer to form the recess.

[0009] Optionally, the forming the upper electrode on the piezoelectric layer comprises: depositing the upper electrode on the piezoelectric layer, the thickness of the deposited upper electrode being greater than or equal to the sum of the thickness of the upper electrode to be formed and the depth of the deepest recess of each of the resonators.

[0010] Optionally, the planarizing the upper surface of the upper electrode comprises: making the upper surface of the upper electrode of each of the resonators flush.

[0011] According to a second aspect, an embodiment of the present application provides a method for manufacturing a resonator, comprising: forming an opening on a substrate surface and filling a sacrificial layer into the opening; forming at least one recess on the sacrificial layer, the depth of the recess being the same as the thickness of a mass load layer to be formed; forming a bottom electrode on the substrate and the sacrificial layer, the bottom electrode filling into part of the recess to form the mass load layer; planarizing an upper surface of the bottom electrode; forming a piezoelectric layer on the bottom electrode; and forming an upper electrode on the piezoelectric layer.

[0012] Optionally, after forming the upper electrode on the piezoelectric layer, the method further comprises: removing the sacrificial layer to form a cavity between the bottom electrode and the substrate.

[0013] Optionally, the resonators are multiple, and the forming the bottom electrode on the substrate and the sacrificial layer comprises: forming multiple separated bottom electrodes, each of which corresponds to one of the resonators; or the forming the bottom electrode on the substrate and the sacrificial layer comprises: forming an integrated bottom electrode, which is shared by multiple of the resonators; or the forming the piezoelectric layer on the bottom electrode comprises: forming multiple separated piezoelectric layers, each of which corresponds to one of the resonators; or the forming the piezoelectric layer on the bottom electrode comprises: forming an integrated piezoelectric layer, which is shared by multiple of the resonators; or the forming the upper electrode on the piezoelectric layer comprises: forming multiple separated upper electrodes, each of which corresponds to one of the resonators; or the forming the upper electrode on the piezoelectric layer comprises: forming an integrated upper electrode, which is shared by multiple of the resonators.

[0014] Optionally, the forming the bottom electrode on the substrate and the sacrificial layer comprises: depositing the bottom electrode on the substrate and the sacrificial layer, and the thickness of the deposited bottom electrode is greater than or equal to the sum of the thickness of the bottom electrode to be formed and the depth of the deepest one of the recesses of the resonators.

[0015] Optionally, the planarizing the upper surface of the bottom electrode comprises: planarizing the upper surface of the bottom electrode of each of the resonators to the same height.

[0016] According to a third aspect, an embodiment of the present application provides a manufacturing method of a filter, comprising: forming at least two resonators according to the method of any one of the first aspect or the second aspect.

[0017] According to a fourth aspect, an embodiment of the present application provides a filter, comprising at least two resonators, at least one of the at least two resonators comprising: a bottom electrode; a piezoelectric layer disposed on the bottom electrode, the piezoelectric layer being formed with at least one recess on the side away from the bottom electrode; and an upper electrode disposed on the piezoelectric layer and filling the recess; wherein the upper surfaces of the upper electrodes of the resonators are planarized to the same height.

[0018] According to a fifth aspect, an embodiment of the present application provides a filter, comprising at least two resonators, at least one of the at least two resonators comprising: a bottom electrode disposed on a substrate, a cavity being formed between the bottom electrode and the substrate, the bottom electrode having at least one protrusion protruding towards the cavity, a height of the protrusion protruding towards the cavity being less than a depth of the cavity; a piezoelectric layer disposed on the bottom electrode; an upper electrode disposed on the piezoelectric layer; wherein upper surfaces of the bottom electrodes of the resonators are flush.

[0019] Optionally, the upper electrode comprises metal molybdenum; or the bottom electrode comprises metal molybdenum; or the piezoelectric layer comprises aluminum nitride.

[0020] Optionally, the recess or the protrusion is regular or irregular in shape; or the recess or the protrusion is symmetrically or asymmetrically arranged.

[0021] Optionally, the recess or the protrusion is disposed at a central region of the corresponding bottom electrode of each resonator, or a center of the recess or the protrusion is not more than 1 / 4 of a wavelength of a resonant wave generated by the resonator away from a center of the corresponding bottom electrode of each resonator.

[0022] The resonator, the filter and the manufacturing method according to the embodiments of the present application have the following advantages: since the mass loading layer is formed in the recess and integrally formed with the upper electrode, the mass loading layer has good combination with the upper electrode and will not have the risk of delamination; the mass loading layer of each resonator is formed in the recess, which increases the mass of the mass loading layer and reduces the thickness of the piezoelectric layer at the same time, and the piezoelectric layer and the mass loading layer are adjusted, so that the resonant frequency is more flexible to adjust; and since the thickness of the piezoelectric layer is reduced, an extremely thin mass loading layer does not need to be formed, and the mass of the mass loading layer can be guaranteed.

[0023] The resonator, the filter and the manufacturing method according to another embodiment of the present application have the following advantages: since the mass loading layer is integrally formed with the bottom electrode, the mass loading layer has good combination with the bottom electrode and will not have the risk of delamination. BRIEF DESCRIPTION OF DRAWINGS

[0024] The features and advantages of the present application will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, which are given by way of illustration and are not to be considered limiting of the present application, in which:

[0025] Figure 1A and Figure 1B A schematic diagram showing a method for setting a mass loading layer for a resonator in the prior art is shown;

[0026] Figure 2 A schematic diagram showing a filter according to an embodiment of the present application is shown.

[0027] Figure 3 Schematic diagram showing an alternative embodiment of a filter according to an embodiment of the present invention;

[0028] Figure 4 Schematic diagram showing a filter according to another embodiment of the present invention;

[0029] Figure 5 Schematic diagram showing an alternative embodiment of a filter according to another embodiment of the present invention;

[0030] Figures 6A to 6G Schematic diagrams showing the respective steps in the manufacturing method of a resonator according to an embodiment of the present invention;

[0031] Figures 7A to 7F Schematic diagrams showing the respective steps in the manufacturing method of a resonator according to another embodiment of the present invention. Detailed implementation manners

[0032] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] Figure 2 Schematic diagram showing a filter according to an embodiment of the present invention, the resonator may include at least two resonators, and in Figure 2 the example, 3 resonators are provided, namely resonator 20A, 20B and 20C. Those skilled in the art should understand that it is also feasible to provide more or fewer resonators. Each resonator includes a bottom electrode 23, a piezoelectric layer 24 and a top electrode 26. Among them, the bottom electrode 23 is disposed on a substrate 21, the piezoelectric layer 24 is disposed on the bottom electrode 23, and the top electrode 26 is disposed on the piezoelectric layer 24. In order to improve the resonance effect of the resonator, a cavity 22 is formed between the bottom electrode 23 of each resonator and the substrate 21. In Figure 2 the example, a cavity is etched on the substrate to implement an acoustic reflection structure. Those skilled in the art should understand that a Bragg reflection layer can also be used to implement the acoustic reflection, and the acoustic reflection structure can be disposed inside the substrate or on the surface of the substrate.

[0034] In Figure 2In the example shown in FIG. 2, the resonator 20A is not provided with a mass load layer, while the resonators 20B and 20C are provided with mass load layers. The piezoelectric layer 24 of the resonators 20B and 20C is formed with a recess 25 on the side away from the bottom electrode 23, and the upper electrode 26 fills the recess 25. The portion of the upper electrode 26 that fills the recess 25 becomes the mass load layer of the resonator, and the upper surfaces of the upper electrodes 26 of the respective resonators are flush with each other. As an alternative, the substrate can be a silicon substrate, the bottom electrode 23 can include molybdenum, the piezoelectric layer 24 can include aluminum nitride, and the upper electrode 26 can include molybdenum.

[0035] Note that, in the example shown in FIG. 2, the bottom electrodes 23 of the respective resonators are separate, while the piezoelectric layers 24 and the upper electrodes 26 are integral. However, the present application is not limited to this, and the piezoelectric layers 24 or the upper electrodes 26 of the respective resonators can be separate, or the bottom electrodes 23 of the respective resonators can be integral while the upper electrodes 26 are separate. Figure 2

[0036] Since the respective resonators have different mass load layers, the respective resonators have different resonant frequencies. In general, the greater the mass of the mass load layer, the lower the resonant frequency of the resonator, and the thicker the piezoelectric layer, the lower the resonant frequency of the resonator. In the example shown in FIG. 2, the resonators 20B and 20C have different depths of the recesses, so that the mass of the mass load layer of the resonators 20B and 20C is different, and the thickness of the piezoelectric layer is also different, and thus the resonators 20B and 20C have different resonant frequencies, which are also different from the resonant frequency of the resonator 20A. As an alternative, the respective resonators can have different widths of the recesses, so that the mass of the mass load layer of the respective resonators is different, and thus the respective resonators have different resonant frequencies. Figure 2 As an alternative, as shown in FIG. 3, each resonator can have a plurality of recesses 25, and the number of recesses of the respective resonators can be the same or different. Similarly, the depth and / or width of the respective recesses can be the same or different. Thus, the mass of the mass load layer of the respective resonators can be made different, and thus the respective resonators have different resonant frequencies.

[0037] Figure 3

[0038] ​​​Further, the recess 25 in the above embodiments can be regular shapes, such as rectangular or circular, or the recess 25 can also be irregular shapes, such as irregular pentagon, etc. Further, the recess 25 of each resonator can also be further arranged symmetrically or asymmetrically. Further, the recess 25 can be arranged at the center region of the corresponding separate electrode of each resonator, or the center of the recess 25 can be arranged at a distance of not more than 1 / 4 of the wavelength of the resonant wave generated by the resonator from the center of the separate electrode.

[0039] Compared with the existing filter preparation method, in the filter of the embodiment of the present application, the mass load layer is formed in the recess and integrally formed with the upper electrode, so the combination of the mass load layer and the upper electrode is good and there is no risk of delamination, and the mass load layer of each resonator is formed in the recess, which reduces the thickness of the piezoelectric layer while increasing the mass of the mass load layer, and the piezoelectric layer and the mass load layer are adjusted, so the adjustment of the resonant frequency is more flexible. In addition, in the prior art, when the mass load layer is formed on the upper electrode alone, if the mass load layer is thin, the processing process will have certain defects, and the mass of the thin mass load layer is also difficult to guarantee. In the filter of the embodiment of the present application, the thickness of the piezoelectric layer is reduced, and when the resonant frequency of the resonator is adjusted to the same resonant frequency as the prior art scheme of forming the mass load layer alone, the thickness of the mass load layer to be formed is greater than the thickness of the mass load layer formed alone in the prior art. Therefore, the filter of the embodiment of the present application can not form an extremely thin mass load layer, which improves the process implementation degree, and the mass of the formed mass load layer can be guaranteed.

[0040] Figure 4 A filter according to another embodiment of the present application is shown, which can include at least two resonators, in which Figure 4 In the example shown, three resonators, i.e. resonators 30A, 30B and 30C, are arranged, and a person skilled in the art can choose to arrange more or fewer resonators. As in the embodiment shown in Figure 2 Each resonator includes a bottom electrode 33, a piezoelectric layer 35 and an upper electrode 36, wherein the bottom electrode 33 is arranged on the substrate 31, the piezoelectric layer 35 is arranged on the bottom electrode 33, and the upper electrode 36 is arranged on the piezoelectric layer 35. In order to improve the resonant effect of the resonator, a cavity 32 is formed between the bottom electrode 33 and the substrate 31 of each resonator. Similarly, in the example shown, the cavity is etched on the substrate to realize the acoustic reflection structure, and a person skilled in the art should understand that the Bragg reflection layer can also be used to realize the acoustic reflection, and the acoustic reflection structure can be arranged in the substrate or on the surface of the substrate. Figure 4

[0041] In the example shown, the cavity is etched on the substrate to realize the acoustic reflection structure, and a person skilled in the art should understand that the Bragg reflection layer can also be used to realize the acoustic reflection, and the acoustic reflection structure can be arranged in the substrate or on the surface of the substrate. Figure 4 ​In the example shown in FIG. 1, the resonator 30A is not provided with a mass load layer, while the resonators 30B and 30C are provided with mass load layers. The bottom electrode 33 of the resonators 30B and 30C has a protrusion 34 protruding toward the cavity 32, and the height of the protrusion 34 protruding toward the cavity 32 is smaller than the depth of the cavity 32. The protrusion 34 of the bottom electrode 33 becomes the mass load layer of the resonator, and the upper surfaces of the bottom electrodes 33 of the respective resonators are flush with each other. As an alternative, the substrate can be a silicon substrate, the bottom electrode 33 can include molybdenum, the piezoelectric layer 35 can include aluminum nitride, and the upper electrode 36 can include molybdenum.

[0042] In the example shown in FIG. 1, the resonator 30A is not provided with a mass load layer, while the resonators 30B and 30C are provided with mass load layers. The bottom electrode 33 of the resonators 30B and 30C has a protrusion 34 protruding toward the cavity 32, and the height of the protrusion 34 protruding toward the cavity 32 is smaller than the depth of the cavity 32. The protrusion 34 of the bottom electrode 33 becomes the mass load layer of the resonator, and the upper surfaces of the bottom electrodes 33 of the respective resonators are flush with each other. As an alternative, the substrate can be a silicon substrate, the bottom electrode 33 can include molybdenum, the piezoelectric layer 35 can include aluminum nitride, and the upper electrode 36 can include molybdenum. Figure 4 In the example shown in FIG. 1, the resonator 30A is not provided with a mass load layer, while the resonators 30B and 30C are provided with mass load layers. The bottom electrode 33 of the resonators 30B and 30C has a protrusion 34 protruding toward the cavity 32, and the height of the protrusion 34 protruding toward the cavity 32 is smaller than the depth of the cavity 32. The protrusion 34 of the bottom electrode 33 becomes the mass load layer of the resonator, and the upper surfaces of the bottom electrodes 33 of the respective resonators are flush with each other. As an alternative, the substrate can be a silicon substrate, the bottom electrode 33 can include molybdenum, the piezoelectric layer 35 can include aluminum nitride, and the upper electrode 36 can include molybdenum.

[0043] In the example shown in FIG. 1, the resonator 30A is not provided with a mass load layer, while the resonators 30B and 30C are provided with mass load layers. The bottom electrode 33 of the resonators 30B and 30C has a protrusion 34 protruding toward the cavity 32, and the height of the protrusion 34 protruding toward the cavity 32 is smaller than the depth of the cavity 32. The protrusion 34 of the bottom electrode 33 becomes the mass load layer of the resonator, and the upper surfaces of the bottom electrodes 33 of the respective resonators are flush with each other. As an alternative, the substrate can be a silicon substrate, the bottom electrode 33 can include molybdenum, the piezoelectric layer 35 can include aluminum nitride, and the upper electrode 36 can include molybdenum. Figure 4 In the example shown in FIG. 1, the resonator 30A is not provided with a mass load layer, while the resonators 30B and 30C are provided with mass load layers. The bottom electrode 33 of the resonators 30B and 30C has a protrusion 34 protruding toward the cavity 32, and the height of the protrusion 34 protruding toward the cavity 32 is smaller than the depth of the cavity 32. The protrusion 34 of the bottom electrode 33 becomes the mass load layer of the resonator, and the upper surfaces of the bottom electrodes 33 of the respective resonators are flush with each other. As an alternative, the substrate can be a silicon substrate, the bottom electrode 33 can include molybdenum, the piezoelectric layer 35 can include aluminum nitride, and the upper electrode 36 can include molybdenum.

[0044] As an alternative, as shown in FIG. 2, each resonator can have a plurality of protrusions 34, and the number of protrusions of the respective resonators can be the same or different. Also, the height and / or width of the respective protrusions can be the same or different. Thus, the mass of the mass load layer of the respective resonators can be made different, and the resonators can have different resonance frequencies. Figure 5

[0045] Further, the protrusions 34 in the above-described embodiments can have a regular shape, such as a rectangular shape or a circular shape, or the protrusions 34 can have an irregular shape, such as an irregular pentagonal shape. Further, when each resonator has a plurality of protrusions 34, the protrusions 34 can be arranged symmetrically or asymmetrically. Further, the distance between the center of the protrusion 34 and the center of the cavity 32 is not greater than 1 / 4 of the wavelength of the resonance wave generated by the resonator.

[0046] In the filter of the present embodiment, the mass load layer is formed integrally with the bottom electrode, and thus the mass load layer and the bottom electrode have good adhesion and do not have the risk of delamination.​

[0047] In the following, the manufacturing method of the resonator according to the embodiments of the present application will be described in detail with reference to the accompanying drawings, which can include the following steps:

[0048] S11. As shown in FIG. 1, a plurality of openings are formed on the surface of a substrate 21, and a sacrificial layer 27 is filled into the openings, wherein the substrate 21 can be a silicon substrate for example, and the sacrificial layer 27 can be a phosphosilicate glass (PSG) for example. Figure 6A

[0049] In the example of FIG. 1, three openings are shown to form resonators 20A, 20B and 20C respectively, and it should be understood by those skilled in the art that more or less resonators can also be formed. Figure 6A In addition, as described above, the embodiments of the present application are described by taking the example of forming cavities on the substrate to achieve the acoustic reflection structure, and it should be understood by those skilled in the art that the Bragg reflection layer can also be used to achieve acoustic reflection, and the acoustic reflection structure can be disposed in the substrate or on the surface of the substrate.

[0050] S12. As shown in FIG. 2, a bottom electrode 23 is formed on the substrate 21 and the sacrificial layer 27.

[0051] Figure 6B In the example of FIG. 2, the bottom electrodes 23 of the respective resonators are separate, and it should be understood by those skilled in the art that the bottom electrodes 23 of the respective resonators can also be integrated, and the integrated bottom electrode is shared by the respective resonators. In an alternative embodiment, the bottom electrode 23 can include molybdenum.

[0052] In the example of FIG. 2, the bottom electrodes 23 of the respective resonators are separate, and it should be understood by those skilled in the art that the bottom electrodes 23 of the respective resonators can also be integrated, and the integrated bottom electrode is shared by the respective resonators. In an alternative embodiment, the bottom electrode 23 can include molybdenum. Figure 6B S13. As shown in FIG. 3, a piezoelectric layer 24 is formed on the bottom electrode 23.

[0053] Figure 6B In the example of FIG. 3, the piezoelectric layers 24 of the respective resonators are integrated, and the integrated piezoelectric layer is shared by the respective resonators, and it should be understood by those skilled in the art that the piezoelectric layer 24 can also be separate. In an alternative embodiment, the piezoelectric layer 24 can include aluminum nitride.

[0054] In the example of FIG. 3, the piezoelectric layers 24 of the respective resonators are integrated, and the integrated piezoelectric layer is shared by the respective resonators, and it should be understood by those skilled in the art that the piezoelectric layer 24 can also be separate. In an alternative embodiment, the piezoelectric layer 24 can include aluminum nitride. Figure 6B S14. As shown in FIG. 4, a mask layer 28 is formed on the piezoelectric layer 24, and part of the mask layer 28 is removed to expose part of the surface of the piezoelectric layer 24 where the recess is to be formed. The mask layer 28 can be made of silicon oxide for example.

[0055] Figure 6B In the example of FIG. 4, it is necessary to form a mass load layer in the resonator 20B, so as to expose part of the surface of the piezoelectric layer 24 of the resonator 20B.

[0056] In the example of FIG. 4, it is necessary to form a mass load layer in the resonator 20B, so as to expose part of the surface of the piezoelectric layer 24 of the resonator 20B. Figure 6B ​​​​​

[0057] S15. Figure 6C As shown, a portion of the exposed surface of the piezoelectric layer 24 is etched to form a recess 25, and then the mask layer 28 is removed. For example, a trim process can be used to form the recess 25 to the desired depth, the depth of which is the same as the thickness of the mass load layer to be formed. For example, hydrofluoric acid can be used to remove the mask layer 28; hydrofluoric acid is highly corrosive to silicon oxide but will not corrode the piezoelectric layer 24.

[0058] exist Figure 6C In the example, a recess 25 is formed on a portion of the surface of the piezoelectric layer 24 of the resonator 20B.

[0059] S16. For example Figure 6D As shown, the same method can be used to form a recess 25 of another depth.

[0060] exist Figure 6D In the example, a recess 25 is formed on a portion of the surface of the piezoelectric layer 24 of the resonator 20C. Those skilled in the art will understand that this step is optional and is unnecessary if only one resonator needs a recess, or if all resonators requiring recesses have the same resonant frequency. For example, if the resonators 20B and 20C requiring recesses have the same resonant frequency, portions of the piezoelectric layer 24 of both resonators 20B and 20C can be exposed simultaneously, and the exposed surfaces of the piezoelectric layer 24 can be etched to form recesses of the same depth.

[0061] As an alternative implementation, when the resonant frequencies of the resonators that need to form recesses are different, the recesses can be formed simultaneously. If the resonant frequencies of the resonators 20B and 20C that need to form recesses are different, the areas of the exposed piezoelectric layer 24 of the resonators 20B and 20C can be different, for example, the widths can be different. This results in the recesses having the same depth but different bottom areas, and consequently, different masses of the upper electrode portion filling each recess. This also allows each resonator to have different resonant frequencies.

[0062] As an optional implementation method, refer to Figure 3 In the embodiment shown, at least one recess can be formed on the surface of the piezoelectric layer corresponding to each resonator.

[0063] S17. For example Figure 6E As shown, an upper electrode 26 is formed on the piezoelectric layer 24. For example, the upper electrode 26 can be formed by deposition. The portion of the upper electrode 26 filling the recess 25 forms a mass load layer. Because the upper electrode 26 partially fills the recess 25, the upper surface of the formed upper electrode 26 is uneven.Figure 6E In the example, because recesses are formed in resonators 20B and 20C, the upper surfaces of the upper electrodes 26 of resonators 20B and 20C are uneven.

[0064] exist Figure 6E In the example, the upper electrode 26 of each resonator is integral, and all resonators share this integral upper electrode. Those skilled in the art will understand that the upper electrode 26 can also be separate. In an alternative embodiment, the upper electrode 26 may include molybdenum.

[0065] S18. For example Figure 6F As shown, the upper surface of each upper electrode 26 is flattened.

[0066] As an alternative implementation, in order to ultimately obtain an upper electrode of a predetermined thickness, the thickness of the deposited upper electrode 26 needs to be greater than or equal to the sum of the thickness of the upper electrode to be formed and the depth of the deepest of each recess.

[0067] For example, when the predetermined thickness of the upper electrode to be formed is h, the depth of the recess in resonator 20B is h1, the depth of the recess in resonator 20C is h2, and h2>h1, it can be predicted that... Figure 6E The upper surface of the upper electrode of resonator 20B has a recess of depth h1, and the upper surface of the upper electrode of resonator 20C has a recess of depth h2. To flatten the upper surface of the upper electrode, at least the height h2 needs to be removed from the upper electrode. Therefore, in Figure 6E In the example, the thickness of the deposited upper electrode 26 should be greater than or equal to h+h2.

[0068] S19. For example Figure 6G As shown, the sacrificial layer is removed so that a cavity 22 is formed between the bottom electrode 23 and the substrate 21, thereby improving the resonance effect of each resonator.

[0069] In the resonator manufacturing method of this invention, compared with existing resonator fabrication methods, since the mass load layer is formed within the recess and integrally formed with the upper electrode, the bonding between the mass load layer and the upper electrode is good, eliminating the risk of delamination. Furthermore, the mass load layer being formed within the recess increases the mass of the mass load layer while reducing the thickness of the piezoelectric layer. Simultaneously, adjustments to both the piezoelectric layer and the mass load layer allow for more flexible adjustment of the resonant frequency. In addition, in the prior art, when the mass load layer is formed separately on the upper electrode, if the mass load layer is thin, certain defects in the processing technology may occur, and the quality of a thin mass load layer is difficult to guarantee. However, in the resonator manufacturing method of this invention, because the thickness of the piezoelectric layer is reduced, when the resonant frequency of the resonator is adjusted to the same resonant frequency as the prior art method of forming the mass load layer separately, the required thickness of the mass load layer is greater than that of the prior art method of forming the mass load layer separately. Therefore, the resonator manufacturing method of this invention does not require forming an extremely thin mass load layer, improving process feasibility, and ensuring the quality of the formed mass load layer.

[0070] Figures 7A to 7F A method for manufacturing a resonator according to another embodiment of the present invention is shown, the method comprising the following steps:

[0071] S21. As Figure 7A As shown, a plurality of openings are formed on the surface of substrate 31, and a sacrificial layer 37 is filled into the openings. The substrate 31 may be, for example, a silicon substrate, and the sacrificial layer 37 may be, for example, phosphosilicate glass (PSG).

[0072] exist Figure 7A In the example shown, three openings are provided for forming resonators 30A, 30B and 30C, respectively. Those skilled in the art will understand that more or fewer resonators may also be formed.

[0073] Similarly, in this embodiment, the acoustic reflection structure is achieved by etching a cavity on the substrate to illustrate the present invention. Those skilled in the art should understand that a Bragg reflector layer can also be used to achieve acoustic reflection, and the acoustic reflection structure can be disposed inside the substrate or on the surface of the substrate.

[0074] S22. For example Figure 7B As shown, a recess 34 is formed on the sacrificial layer 37, and the depth of the recess 34 is the same as the thickness of the mass load layer to be formed.

[0075] and Figures 6A to 6GThe corresponding embodiment is similar, a patterned mask layer can be formed on the substrate 31 and the sacrificial layer 37 to expose the surface of the sacrificial layer 37 to be formed into the recess 34, so that the recess 34 with the desired depth can be formed by etching, and then the mask layer is removed by hydrofluoric acid or the like. If recesses 34 with different depths are needed, the above steps need to be repeated, and if recesses 34 with the same depth are needed, recesses with the same depth can be formed at the same time.

[0076] As an optional embodiment, referring to the embodiment shown in Figure 5 , at least one recess can be formed on the surface of the sacrificial layer corresponding to each resonator.

[0077] S23. As shown in Figure 7C , a bottom electrode 33 is formed on the substrate 31 and the sacrificial layer 37, for example, the bottom electrode 33 can be formed by deposition, and the part of the bottom electrode 33 filling into the recess 34 forms a mass loading layer. Since the bottom electrode 33 fills part of the recess 34, the upper surface of the formed bottom electrode 33 is uneven. In Figure 7C , since recesses are formed in the resonator 30B and the resonator 30C, the upper surface of the bottom electrode 33 of the resonator 30B and the resonator 30C is uneven.

[0078] In Figure 7C , the bottom electrode 33 of each resonator is separate, and those skilled in the art should understand that the bottom electrode 33 of each resonator can also be integrated, and each resonator shares the integrated bottom electrode. In an optional embodiment, the bottom electrode 33 can include metallic molybdenum.

[0079] S24. As shown in Figure 7D , the upper surface of each bottom electrode 34 is planarized.

[0080] As an optional embodiment, in order to finally obtain a bottom electrode with a predetermined thickness, the thickness of the deposited bottom electrode needs to be greater than or equal to the sum of the thickness of the bottom electrode to be formed and the depth of the deepest recess in each recess.

[0081] For example, when the predetermined thickness of the bottom electrode to be formed is h, the depth of the recess of the resonator 30B is h1, the depth of the recess of the resonator 30C is h2, and h2>h1, it can be foreseen that Figure 7C the upper surface of the bottom electrode of the resonator 30B has a recess with a depth of h1, and the upper surface of the bottom electrode of the resonator 30C has a recess with a depth of h2. In order to planarize the upper surface of the bottom electrode, at least the height of the bottom electrode needs to be removed h2, so in Figure 7C , the thickness of the deposited bottom electrode should be greater than or equal to h+h2.

[0082] S25. For example Figure 7E As shown, a piezoelectric layer 35 is formed on the bottom electrode 33.

[0083] exist Figure 7E In the example, the piezoelectric layer 35 of each resonator is integral, and all resonators share this integral piezoelectric layer. Those skilled in the art will understand that the piezoelectric layer 35 can also be discrete. In an alternative embodiment, the piezoelectric layer 35 may include aluminum nitride.

[0084] S26. For example Figure 7E As shown, an upper electrode 36 is formed on the piezoelectric layer 35.

[0085] exist Figure 7E In the example, the upper electrode 36 of each resonator is integral, and all resonators share this integral upper electrode. Those skilled in the art will understand that the upper electrode 36 can also be separate. In an alternative embodiment, the upper electrode 36 may include molybdenum.

[0086] S27. For example Figure 7F As shown, the sacrificial layer is removed so that a cavity 32 is formed between the bottom electrode 33 and the substrate 31, thereby improving the resonance effect of each resonator.

[0087] In the resonator manufacturing method of this embodiment, compared with the existing resonator fabrication method, since the mass load layer and the bottom electrode are integrally formed, the mass load layer and the bottom electrode have good bonding and there is no risk of delamination.

[0088] Furthermore, embodiments of the present invention also provide a method for manufacturing a filter, which can employ the above-described method. Figures 6A to 6G The embodiments shown, or those described above Figures 7A to 7F The manufacturing method of the illustrated embodiment forms at least two resonators. Specific details of the manufacturing method of the filter according to the embodiments of the present invention can be found in the corresponding references. Figures 6A to 6G Or Figures 7A to 7F The relevant descriptions and effects in the illustrated embodiments are for understanding purposes only and will not be repeated here. Optionally, the mass load layers of at least two resonators formed by the filter manufacturing method provided in the embodiments of the present invention are all different, so that the resonant frequencies of each resonator are also different.

[0089] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A method of manufacturing a resonator, characterized by, The method comprises: forming at least two resonators, one of which is not provided with a mass load layer, and at least one of which is provided with a mass load layer, comprising, forming a bottom electrode; forming a piezoelectric layer on the bottom electrode; forming at least one recess on the piezoelectric layer, the depth of the recess being the same as the thickness of the mass load layer to be formed; forming an upper electrode on the piezoelectric layer, the part of the upper electrode filling into the recess forming the mass load layer, and the upper surface of the upper electrode of each resonator being planarized so that the upper surfaces of the upper electrodes of the resonators are flush with each other; the recess is arranged at the center region of the bottom electrode corresponding to each resonator, or the center of the recess is not more than 1 / 4 of the wavelength of the resonant wave generated by the resonator from the center of the bottom electrode corresponding to each resonator.

2. The method of claim 1, wherein, Before the bottom electrode is formed, it further comprises: forming at least one opening on the surface of the substrate; filling a sacrificial layer in the opening; after the upper surface of the upper electrode is planarized, it further comprises: removing the sacrificial layer to form a cavity between the bottom electrode and the substrate.

3. The method of claim 1, wherein, The resonators are multiple, the forming of the bottom electrode comprises: forming multiple separate bottom electrodes, each of which corresponds to one of the resonators; or the forming of the bottom electrode comprises: forming an integral bottom electrode, and multiple resonators share the integral bottom electrode; or the forming of the piezoelectric layer on the bottom electrode comprises: forming multiple separate piezoelectric layers, each of which corresponds to one of the resonators; or the forming of the piezoelectric layer on the bottom electrode comprises: forming an integral piezoelectric layer, and multiple resonators share the integral piezoelectric layer; or the forming of the upper electrode on the piezoelectric layer comprises: forming multiple separate upper electrodes, each of which corresponds to one of the resonators; or the forming of the upper electrode on the piezoelectric layer comprises: forming an integral upper electrode, and multiple resonators share the integral upper electrode.

4. The method of claim 3, wherein, The forming of the at least one recess on the piezoelectric layer comprises: forming a mask layer on the piezoelectric layer; removing part of the mask layer on the piezoelectric layer corresponding to the resonator where the mass load layer is to be formed, to expose part of the surface of the piezoelectric layer where the recess is to be formed; etching the exposed part of the surface of the piezoelectric layer to form the recess.

5. The method of claim 3, wherein, The forming of the upper electrode on the piezoelectric layer comprises: depositing the upper electrode on the piezoelectric layer, the thickness of the deposited upper electrode being greater than or equal to the sum of the thickness of the upper electrode to be formed and the depth of the deepest recess of each resonator.

6. The method according to any one of claims 1-5, characterized in that, The planarization of the upper surface of the upper electrode of each resonator comprises: making the upper surfaces of the upper electrodes of the resonators flush with each other.

7. A method of manufacturing a resonator, characterized by, The method comprises: forming at least two resonators, one of which is not provided with a mass load layer, and at least one of which is provided with a mass load layer, comprising, forming an opening on the surface of the substrate, and filling a sacrificial layer into the opening; forming at least one recess on the sacrificial layer, the depth of the recess being the same as the thickness of the mass load layer to be formed; forming a bottom electrode on the substrate and the sacrificial layer, the bottom electrode filling into the part of the recess to form the mass load layer; planarizing the upper surface of the bottom electrode of each of the resonators so that the upper surface of the bottom electrode of each resonator is flush; forming a piezoelectric layer on the bottom electrode; forming an upper electrode on the piezoelectric layer; the recess is arranged at the center region of the bottom electrode corresponding to each resonator, or the distance between the center of the recess and the center of the bottom electrode corresponding to each resonator is not greater than 1 / 4 of the wavelength of the resonant wave generated by the resonator.

8. The method of claim 7, wherein, after forming the upper electrode on the piezoelectric layer, further comprising: removing the sacrificial layer to form a cavity between the bottom electrode and the substrate.

9. The method of claim 7, wherein, the resonators are a plurality of, the forming of the bottom electrode on the substrate and the sacrificial layer comprises: forming a plurality of separate bottom electrodes, each of the bottom electrodes corresponding to one of the resonators; or the forming of the bottom electrode on the substrate and the sacrificial layer comprises: forming an integral bottom electrode, and the plurality of resonators share the integral bottom electrode; or the forming of the piezoelectric layer on the bottom electrode comprises: forming a plurality of separate piezoelectric layers, each of the piezoelectric layers corresponding to one of the resonators; or the forming of the piezoelectric layer on the bottom electrode comprises: forming an integral piezoelectric layer, and the plurality of resonators share the integral piezoelectric layer; or the forming of the upper electrode on the piezoelectric layer comprises: forming a plurality of separate upper electrodes, each of the upper electrodes corresponding to one of the resonators; or the forming of the upper electrode on the piezoelectric layer comprises: forming an integral upper electrode, and the plurality of resonators share the integral upper electrode.

10. The method of claim 9, wherein, the forming of the bottom electrode on the substrate and the sacrificial layer comprises: depositing the bottom electrode on the substrate and the sacrificial layer, and the thickness of the deposited bottom electrode is greater than or equal to the sum of the thickness of the to-be-formed bottom electrode and the depth of the deepest recess of each resonator.

11. The method according to any one of claims 7-10, characterized in that, the planarizing of the upper surface of the bottom electrode of each of the resonators comprises: the upper surface of the bottom electrode of each of the resonators is flush.

12. A filter, characterized by comprising at least two resonators, one of which does not have a mass load layer, at least one of the at least two resonators has a mass load layer, comprising: a bottom electrode; a piezoelectric layer arranged on the bottom electrode, the piezoelectric layer being formed with at least one recess on the side away from the bottom electrode; an upper electrode arranged on the piezoelectric layer and filling the recess, the part of the upper electrode filling into the recess becoming a mass load layer; wherein the upper surfaces of the upper electrodes of each of the resonators are flush; the recess is arranged at the center region of the bottom electrode corresponding to each resonator, or the distance between the center of the recess and the center of the bottom electrode corresponding to each resonator is not greater than 1 / 4 of the wavelength of the resonant wave generated by the resonator.

13. A filter, characterized by comprising at least two resonators, one of which does not have a mass load layer, at least one of the at least two resonators has a mass load layer, comprising: a bottom electrode; A bottom electrode is arranged on a substrate, a cavity is formed between the bottom electrode and the substrate, the bottom electrode has at least one protruding part protruding towards the cavity, the height of the protruding part protruding towards the cavity is less than the depth of the cavity, and the protruding part of the bottom electrode becomes a mass loading layer; A piezoelectric layer is arranged on the bottom electrode; An upper electrode is arranged on the piezoelectric layer; The upper surfaces of the bottom electrodes of each resonator are flush with each other; The protruding part is arranged at the center region of the bottom electrode corresponding to each resonator, or the distance between the center of the protruding part and the center of the bottom electrode corresponding to each resonator is not greater than 1 / 4 of the wavelength of the resonant wave generated by the resonator.

14. The filter according to claim 12 or 13, characterized in that, The upper electrode comprises metal molybdenum; or the bottom electrode comprises metal molybdenum; or the piezoelectric layer comprises aluminum nitride.

15. The filter of claim 12, wherein, The recessed part is regular or irregular in shape; or the recessed part is symmetrically or asymmetrically arranged.

16. The filter of claim 13, wherein, The protruding part is regular or irregular in shape; or the protruding part is symmetrically or asymmetrically arranged.

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