Filter and Method for Forming the Same, and Electronic Device

Abstract

A filter, a method for forming the same, and an electronic device. The filter includes: an interconnection window in a protective layer; a pad located in the interconnection window, with the sidewall of the pad aligned with the sidewall of the interconnection window, and the pad electrically connected to a connection portion. Since the sidewall of the pad is aligned with the sidewall of the interconnection window, and the interconnection window is located in the protective layer, that is, in this embodiment, only one photomask is used to form the pad and the interconnection window. Compared with the solution of using two photomasks to form the pad and the interconnection window respectively, the number of photomasks is reduced, and the production cost is correspondingly reduced. Moreover, this also improves the alignment accuracy between the interconnection window and the pad. In addition, since the protective layer covers the interdigital transducer, the connection portion, and the substrate, the protective layer can protect the interdigital transducer, the connection portion, and the substrate, thereby facilitating reducing the probability of damage to the interdigital transducer, the connection portion, or the substrate during the manufacturing process, and further improving the performance of the filter.

Description

Technical Field

[0001] Embodiments of the present invention relate to the field of semiconductor manufacturing, and in particular, to a filter, a method for forming the same, and an electronic device. Background Art

[0002] The radio frequency (RF) front-end chip of a wireless communication device includes a power amplifier, an antenna switch, a radio frequency filter, a multiplexer, a low-noise amplifier, etc. Among them, the radio frequency filter includes a piezoelectric surface acoustic wave (SAW) filter, a piezoelectric bulk acoustic wave (BAW) filter, a micro-electro-mechanical system (MEMS) filter, an integrated passive device (IPD) filter, etc.

[0003] The quality factor value (Q value) of the SAW filter is relatively high, and a radio frequency filter with low insertion loss and high out-of-band rejection is made of the SAW filter. As a filter that is widely used in current wireless communication devices, a highly reliable SAW filter can extend the service life of electronic devices and expand the scope of use.

[0004] Currently, there are still many problems in the method for forming a SAW filter. Summary of the Invention

[0005] The problem solved by the embodiments of the present invention is to provide a filter, a method for forming the same, and an electronic device, which can improve the performance of the filter while reducing the use of photomasks and lowering the production cost.

[0006] To solve the above problems, an embodiment of the present invention provides a method for forming a filter, including: providing a substrate, on which an interdigital transducer and a connection part located on the side of the interdigital transducer are formed, and the connection part is electrically connected to the interdigital transducer; forming a protective material layer on the substrate, and the protective material layer covers the interdigital transducer, the connection part, and the substrate; forming a mask layer with a mask opening on the protective material layer, and the projection of the mask opening on the connection part covers a partial surface of the connection part; using the mask layer as a mask to remove the protective material layer at the bottom of the mask opening, and forming an interconnection window in the protective material layer, and the remaining protective material layer serves as a protective layer; forming a pad in the mask opening, the pad is also located in the interconnection window, the side wall of the pad is aligned with the side wall of the interconnection window, and the pad is electrically connected to the connection part.

[0007] Correspondingly, an embodiment of the present invention further provides a filter, including: a substrate; an interdigital transducer located on the substrate; a connection portion located on the substrate at a side portion of the interdigital transducer, the connection portion being electrically connected to the interdigital transducer; a protective layer covering the interdigital transducer, the connection portion, and the substrate, an interconnection window being formed in the protective layer, and a partial surface of the connection portion being exposed through the interconnection window; and a pad located in the interconnection window, a sidewall of the pad being aligned with a sidewall of the interconnection window, and the pad being electrically connected to the connection portion.

[0008] Correspondingly, the present invention further provides an electronic device including the filter according to any embodiment of the present invention.

[0009] Compared with the prior art, the technical solution of the embodiment of the present invention has the following advantages:

[0010] In a method for forming a filter provided by an embodiment of the present invention, a protective material layer covering the interdigital transducer, the connection portion, and the substrate is formed on the substrate; a mask layer having a mask opening is formed on the protective material layer, a projection of the mask opening on the connection portion covering a partial surface of the connection portion; the protective material layer at the bottom of the mask opening is removed using the mask layer as a mask, an interconnection window is formed in the protective material layer, and the remaining protective material layer serves as a protective layer; a pad is formed in the mask opening, the pad also being located in the interconnection window, a sidewall of the pad being aligned with a sidewall of the interconnection window, and the pad being electrically connected to the connection portion; in this embodiment, in the process of forming the pad, the protective material layer at the bottom of the mask opening is removed using the mask layer as a mask, an interconnection window is formed in the protective material layer, and then the pad is formed in the mask opening, that is, only one photomask is used in this embodiment to form the pad and the interconnection window. Compared with the solution of using two photomasks to separately form the pad and the interconnection window, the number of photomasks is reduced, the production cost is correspondingly reduced, and moreover, the alignment accuracy between the interconnection window and the pad is improved, which is beneficial to improving the performance of the filter; in addition, since the protective material layer is formed first and then the pad is formed, the protective material layer can protect the interdigital transducer, the connection portion, and the substrate, which is beneficial to reducing the probability of damage to the interdigital transducer, the connection portion, or the substrate in subsequent processings, and thus improves the performance of the filter.

[0011] An embodiment of the present invention further provides a filter, including: a substrate; an interdigital transducer located on the substrate; a connecting portion located on the substrate at a side of the interdigital transducer, the connecting portion being electrically connected to the interdigital transducer; a protective layer covering the interdigital transducer, the connecting portion and the substrate, an interconnection window being formed in the protective layer, the interconnection window exposing a partial surface of the connecting portion; a pad located in the interconnection window, a sidewall of the pad being aligned with a sidewall of the interconnection window, and the pad being electrically connected to the connecting portion; in this embodiment, since the sidewall of the pad is aligned with the sidewall of the interconnection window, and the interconnection window is located in the protective layer, that is, only one photomask is used in this embodiment to form the pad and the interconnection window. Compared with the solution of using two photomasks to form the pad and the interconnection window respectively, the number of photomasks is reduced, and the production cost is correspondingly reduced. Moreover, this also improves the alignment accuracy between the interconnection window and the pad, thereby being beneficial to improving the performance of the filter; in addition, since the protective layer covers the interdigital transducer, the connecting portion and the substrate, the protective layer can protect the interdigital transducer, the connecting portion and the substrate, thereby being beneficial to reducing the probability of damage to the interdigital transducer, the connecting portion or the substrate during the manufacturing process, and further improving the performance of the filter. Description of the Drawings

[0012] Figure 1 is a schematic structural diagram of a filter;

[0013] Figure 2 is a schematic structural diagram of another filter;

[0014] Figures 3 to 9 is a schematic structural diagram corresponding to each step in the first embodiment of the method for forming the filter of the present invention;

[0015] Figures 10 to 18 is a schematic structural diagram corresponding to each step in the second embodiment of the method for forming the filter of the present invention;

[0016] Figure 19 is a schematic structural diagram of the first embodiment of the filter of the present invention;

[0017] Figure 20 is a schematic structural diagram of the second embodiment of the filter of the present invention. Detailed Description of the Embodiments

[0018] Currently, there are still many problems in the method for forming a SAW filter. With reference to a schematic structural diagram of a filter, the reasons for the manufacturing process of the filter to be improved are analyzed.

[0019] Figure 1 is a schematic structural diagram of a filter.

[0020] Reference Figure 1, the filter includes: a substrate 10; an interdigital transducer 11 located on the substrate 10; a connecting portion 12 located on the substrate 10 at the side of the interdigital transducer 11, the connecting portion 12 being electrically connected to the interdigital transducer 11; a pad 13 located on a partial surface of the connecting portion 12, the pad 13 being electrically connected to the connecting portion 12; a frequency modulation layer 14 covering the interdigital transducer 11, the pad 13, the substrate 10, and the surface of the connecting portion 12 exposed by the pad 13, and a first interconnect window 16 is provided in the frequency modulation layer 14, and the first interconnect window 16 exposes a partial surface of the pad 13.

[0021] It should be noted that the pad 13 is located on a partial surface of the connecting portion 12. The process of forming the pad 13 requires one photomask. In order to achieve the electrical connection between the pad 13 and an external circuit, another photomask is needed to form the first interconnect window 16 in the frequency modulation layer 14. That is to say, during the manufacturing process, two different photomasks are used to separately form the pad 13 and the first interconnect window 16.

[0022] Figure 2 is a schematic structure of another filter.

[0023] The similarities between the structure of the second filter and the structure of the first filter will not be elaborated here. The differences between the structure of the second filter and the structure of the first filter are as follows: a passivation layer 25 is located between the frequency modulation layer 24 and the interdigital transducer 21, and between the frequency modulation layer 24 and the connecting portion 22. A second interconnect window 27 is provided in the passivation layer 25, and the second interconnect window 27 exposes a partial surface of the connecting portion 22.

[0024] It should be noted that since the passivation layer 25 is located between the frequency modulation layer 24 and the interdigital transducer 21, and between the frequency modulation layer 24 and the connecting portion 22 to protect the interdigital transducer 21. In order to achieve the electrical connection between the connecting portion 22 and the pad 23, one photomask is needed to form the second interconnect window 27 in the passivation layer 25. At the same time, in order to achieve the electrical connection between the pad 23 and an external circuit, another photomask is needed to form the first interconnect window 26 in the frequency modulation layer 24. That is to say, during the manufacturing process, three photomasks are used to separately form the first interconnect window 26, the second interconnect window 27, and the pad 23.

[0025] In summary, in the prior art, both of the above two filters require multiple photomasks to form interconnect windows and pads, thereby increasing the number of lithography times and also increasing the process cost. In addition, due to the limitations of lithography process conditions, during the process of forming pads and interconnect windows, overlay errors are likely to occur, thereby reducing the alignment accuracy between the pads and the interconnect windows, and further affecting the performance of the filter.

[0026] To solve the above technical problems, an embodiment of the present invention provides a method for forming a filter, including: providing a substrate, on which an interdigital transducer and a connection part located at a side part of the interdigital transducer are formed, and the connection part is electrically connected to the interdigital transducer; forming a protective material layer on the substrate, the protective material layer covering the interdigital transducer, the connection part and the substrate; forming a mask layer with a mask opening on the protective material layer, a projection of the mask opening on the connection part covering a partial surface of the connection part; using the mask layer as a mask to remove the protective material layer at the bottom of the mask opening, forming an interconnection window in the protective material layer, and the remaining protective material layer serving as a protective layer; forming a pad in the mask opening, the pad also being located in the interconnection window, a side wall of the pad being aligned with a side wall of the interconnection window, and the pad being electrically connected to the connection part.

[0027] In the solution disclosed in the embodiment of the present invention, during the process of forming the pad, using the mask layer as a mask to remove the protective material layer at the bottom of the mask opening, forming an interconnection window in the protective material layer, and then forming a pad in the mask opening, that is, in this embodiment, only one photomask is used to form the pad and the interconnection window. Compared with the solution of using two photomasks to separately form the pad and the interconnection window, the number of photomasks is reduced, the production cost is correspondingly reduced, and moreover, the alignment accuracy between the interconnection window and the pad is improved, which is beneficial to improving the performance of the filter; in addition, since the protective material layer is formed first and then the pad is formed, the protective material layer can play a protective role for the interdigital transducer, the connection part and the substrate, which is beneficial to reducing the probability of damage to the interdigital transducer, the connection part or the substrate in the subsequent process, and further improving the performance of the filter.

[0028] In order to make the above objects, features and advantages of the embodiments of the present invention more obvious and understandable, the following specifically describes the embodiments of the present invention in detail with reference to the drawings.

[0029] Figures 3 to 9 It is a schematic structural diagram corresponding to each step in the first embodiment of the method for forming a filter of the present invention.

[0030] Refer to Figure 3 , provide a substrate 100, on which an interdigital transducer 101 and a connection part 102 located at a side part of the interdigital transducer 101 are formed, and the connection part 102 is electrically connected to the interdigital transducer 101.

[0031] It should be noted that the electrical connection between the connection part 102 and the interdigital transducer 101 is not shown in the figure. In actual design, the connection part 102 and the interdigital transducer 101 are electrically connected in other areas of the filter.

[0032] The substrate 100 is used to provide a process platform for the subsequent formation of a surface acoustic wave (SAW) filter. The SAW filter is a dedicated filtering device made using the piezoelectric effect and the physical properties of surface acoustic wave propagation. In the SAW filter, the signal undergoes two conversions of electric-acoustic-electric, thereby achieving the frequency selection characteristic. The SAW filter has the advantages of high operating frequency, simple manufacturing process, low manufacturing cost, high consistency of frequency characteristics, etc. Therefore, it is widely used in various electronic devices.

[0033] In this embodiment, the substrate 100 is a piezoelectric substrate, so that the subsequent SAW filter structure can utilize the piezoelectric effect for filtering processing.

[0034] The material of the substrate 100 includes lithium niobate (LiNbO3), lithium tantalate (LiTaO3), quartz, or piezoelectric ceramics. As an example, the material of the substrate 100 is lithium tantalate.

[0035] In other embodiments, the substrate can also be a piezoelectric on insulator (POI) substrate, which includes a piezoelectric material layer, a low sound velocity layer, a high sound velocity layer, and a high-resistance silicon substrate stacked in sequence from top to bottom. Among them, the material of the piezoelectric material layer includes lithium tantalate or lithium niobate, the material of the low sound velocity layer includes silicon oxide, glass, silicon oxynitride, or tantalum oxide, and the material of the high sound velocity layer includes polysilicon, silicon nitride, aluminum oxide, aluminum nitride, or silicon carbide, etc. As an example, the material of the piezoelectric material layer is lithium tantalate, the material of the low sound velocity layer is silicon oxide, and the material of the high sound velocity layer is polysilicon.

[0036] The interdigital transducer 101 (IDT) is used to achieve the mutual conversion between electrical signals and acoustic signals, so that the SAW filter can filter the signals. In this embodiment, the formed filter is a SAW filter. Therefore, the interdigital transducer 101 is correspondingly an interdigital electrode structure, and the interdigital transducer 101 includes a plurality of electrode fingers. Specifically, the interdigital transducer 101 is a metal interdigital transducer.

[0037] The material of the interdigital transducer 101 includes one or more of Mo, Al, Pt, W, Au, Al, Cr, Cu, Ni, and Ag. In this embodiment, the material of the interdigital transducer 101 is aluminum. Specifically, a metal film is deposited on the substrate 100, and the metal film is patterned through photolithography and etching processes to form the interdigital transducer 101.

[0038] The connecting portion 102 is used to realize the electrical connection between the interdigital transducer 101 and the pad, so as to realize the electrical connection between the interdigital transducer 101 and the external circuit structure. Alternatively, the connecting portion 102 can also be used to realize the electrical connection between the interdigital transducers 101 in different regions.

[0039] In this embodiment, the connecting portion 102 and the interdigital transducer 101 are formed in the same step, which is beneficial to reducing the process steps and the process cost. Therefore, in this embodiment, the material of the connecting portion 102 is the same as that of the interdigital transducer 101.

[0040] In this embodiment, the connecting portion 102 includes a first electrode 103 and second electrodes 104 located on both sides of the first electrode 103, and the first electrode 103 and the second electrodes 104 are respectively electrically connected to at least one of the interdigital transducers 101.

[0041] The second electrode 104 is used to realize the electrical connection between the interdigital transducers 101 in different regions.

[0042] Specifically, the connecting portion 102 that needs to be electrically connected to other connecting portions 102 through the pad serves as the second electrode 104.

[0043] The connecting portion 102 located between the second electrodes 104 arranged at adjacent intervals serves as the first electrode 103.

[0044] The first electrode 103 is used to realize the electrical connection between the interdigital transducers 101 in different regions; or, the first electrode 103 is used to be electrically connected to one interdigital transducer 101.

[0045] In this embodiment, the surface acoustic wave filter is a longitudinal coupled dual-mode resonator type (Double Mode SAW, DMS) filter. The DMS filter utilizes the dual-mode characteristics of the surface acoustic wave, and flexibly designs the stopband suppression and bandwidth indexes of the filter by adding a reflector between two interdigital transducers (IDT). Due to its structural characteristics, the DMS filter can provide performance similar to that of a bulk acoustic wave (BAW) filter at low frequencies, with less loss; in addition, in the design of the DMS filter, by changing the key parameters of the circuit topology and introducing new transmission zeros, the out-of-band suppression characteristics in the high-frequency band can be improved. Therefore, it is widely used in various electronic devices.

[0046] In other embodiments, according to actual design requirements, the surface acoustic wave filter can also be other types of filters.

[0047] In this embodiment, the connecting portion 102 further includes a third electrode 105, and the third electrode 105 is electrically connected to at least one of the interdigital transducers 101.

[0048] The third electrode 105 is used as the input end or the output end of the interdigital transducer 101.

[0049] Reference Figure 4 , a protective material layer 106 is formed on the substrate 100, and the protective material layer 106 covers the interdigital transducer 101, the connecting portion 102, and the substrate 100.

[0050] The protective material layer 106 is used to form a protective layer. Moreover, the protective material layer 106 that covers the interdigital transducer 101, the connecting portion 102, and the substrate 100 is formed first, so that in subsequent processes, the protective material layer 106 can protect the interdigital transducer 101, the connecting portion 102, and the substrate 100.

[0051] In this embodiment, the process of forming the protective material layer 106 on the substrate 100 includes a physical vapor deposition process.

[0052] It should be noted that the physical vapor deposition process has the characteristic of high density of film layer deposition. Therefore, the protective material layer 106 formed by the physical vapor deposition process has a higher density, which is beneficial to improving the density of the subsequent formed protective layer.

[0053] In the step of forming the protective material layer 106, the protective material layer 106 at least includes a frequency modulation layer 107.

[0054] In this embodiment, the protective material layer 106 is a single layer.

[0055] Specifically, the protective material layer 106 is the frequency modulation layer 107.

[0056] The frequency modulation layer 107 can not only be used to protect the interdigital transducer 101, the connecting portion 102, and the substrate 100 in subsequent processes, but also be used to adjust the operating frequency of the interdigital transducer 101. Specifically, the operating frequency of the interdigital transducer 101 can be adjusted by changing the thickness of the frequency modulation layer 107.

[0057] In other embodiments, the protective material layer may be a laminate.

[0058] In this embodiment, in the step of forming the protective material layer 106 on the substrate 100, the material of the frequency modulation layer 107 includes silicon oxide.

[0059] It should be noted that silicon oxide has relatively stable physical and chemical properties, and in subsequent process steps, silicon oxide is not easily removed and can play an effective protective role.

[0060] In this embodiment, the thickness of the frequency modulation layer 107 should not be too large or too small. If the thickness of the frequency modulation layer 107 is too large or too small, it is likely to affect the adjustment effect of the frequency modulation layer 107 on the operating frequency of the interdigital transducer 101, and correspondingly, it is likely to cause the operating frequency of the interdigital transducer 101 after frequency modulation to still not meet the actual design requirements. Therefore, in this embodiment, the thickness of the frequency modulation layer 107 is 20 angstroms to 1000 angstroms.

[0061] Reference Figure 5 , after forming the protective material layer 106 on the substrate 100 and before forming the mask layer with a mask opening on the protective material layer 106, it further includes: forming a dielectric layer 109 on the protective material layer 106, and the dielectric layer 109 exposes the protective material layer 106 on a partial surface of the connection portion 102.

[0062] The dielectric layer 109 has insulating properties, which is beneficial to further improving the electrical isolation effect between the connection portion 102 covered by it and the pad.

[0063] The material of the dielectric layer 109 includes one or more of polyimide (PI), silicon oxide, silicon nitride, aluminum oxide, and aluminum nitride. Polyimide, silicon oxide, silicon nitride, aluminum oxide, and aluminum nitride all have good insulating properties. As an example, the material of the dielectric layer 109 is polyimide.

[0064] In this embodiment, in the step of forming the dielectric layer 109 on the protective material layer 106, the dielectric layer 109 spans and covers the protective material layer 106 on the first electrode 103, and exposes at least a partial surface of the protective material layer 106 on the second electrode 104.

[0065] It should be noted that the dielectric layer 109 exposes a partial surface of the protective material layer 106 on the second electrode 104, which is beneficial to subsequent removal of the protective material layer 106 on the second electrode 104, so that the pad is electrically connected to the second electrode 104.

[0066] The dielectric layer 109 spans and covers the protective material layer 106 on the first electrode 103, which is beneficial to improving the electrical isolation effect between the first electrode 103 and the pad.

[0067] As an example, the process of forming the dielectric layer 109 includes a spin coating process. In other embodiments, other suitable deposition processes can also be used to form the dielectric layer.

[0068] Reference Figure 6 , forming a mask layer 111 with a mask opening 110 on the protective material layer 106, and the projection of the mask opening 110 on the connection portion 102 covers a partial surface of the connection portion 102.

[0069] The mask opening 110 is used to define the position and shape of the subsequent pad, and also facilitates the subsequent removal of the protective material layer 106 at the bottom of the mask opening 110 along the mask opening 110.

[0070] The projection of the mask opening 110 on the connecting portion 102 covers a partial surface of the connecting portion 102, facilitating the pad to be electrically connected to the connecting portion 102.

[0071] The mask layer 111 is used as a mask for forming the protective layer and the pad.

[0072] In this embodiment, the material of the mask layer 111 includes photoresist. The photoresist has high resolution, so that the opening size of the mask opening 110 can be precisely controlled; at the same time, the photoresist is easy to be removed, thereby reducing the process complexity and further improving the production efficiency. In other embodiments, other materials that can be used as an etching mask and are easy to be removed can also be selected for the mask layer.

[0073] In this embodiment, in the step of forming the mask layer 111 with the mask opening 110 on the protective material layer 106, the mask opening 110 exposes at least a partial surface of the dielectric layer 109 and a partial surface of the protective material layer 106 exposed by the dielectric layer 109, which is beneficial to increasing the process window for forming the pad, and at the same time reducing the difficulty of subsequent removal of the protective material layer 106 exposed by the dielectric layer 109.

[0074] In one embodiment, the dielectric layer 109 extends across and covers the protective material layer 106 located on the first electrode 103. Therefore, in the step of forming the mask layer 111 with the mask opening 110 on the protective material layer 106, the mask opening 110 extends across the dielectric layer 109, and the mask opening 110 exposes the dielectric layer 109 on the first electrode 103 and partial surfaces of the protective material layer 106 on both sides of the first electrode 103, so as to electrically connect the second electrodes 104 on both sides of the first electrode 103 with the same pad subsequently.

[0075] In this embodiment, the connecting portion 102 further includes a third electrode 105. Therefore, the mask opening 110 also exposes at least a partial surface of the protective material layer 106 on the third electrode 105.

[0076] In this embodiment, the materials of the dielectric layer 109 and the protective material layer 106 satisfy that in the process of etching the protective material layer 106, due to the certain thickness of the dielectric layer 109, the dielectric layer 109 can protect the protective material layer 106 covered by it during the etching of the protective material layer 106. As an example, the thickness of the dielectric layer 109 is 1.8 micrometers to 3 micrometers.

[0077] Reference Figure 7 , using the mask layer 111 as a mask to remove the protective material layer 106 at the bottom of the mask opening 110, an interconnection window 112 is formed in the protective material layer 106, and the remaining protective material layer 106 serves as a protective layer 113.

[0078] The interconnection window 112 is used to provide a spatial position for realizing electrical connection between the pad and the connection part 102.

[0079] The protective layer 113 is used to protect the interdigital transducer 101, the connection part 102 and the substrate 100.

[0080] Specifically, in the step of using the mask layer 111 as a mask to remove the protective material layer 106 at the bottom of the mask opening 110, under the blocking action of the dielectric layer 109, first interconnection windows 114 are formed in the protective material layer 106 on both sides of the first electrode 103, and at least part of the surface of the second electrode 104 is exposed by the first interconnection windows 114.

[0081] At least part of the surface of the second electrode 104 is exposed by the first interconnection windows 114, which facilitates subsequent electrical connection of the second electrodes 104 on both sides of the first electrode 103 through the pad, thereby realizing electrical connection between the interdigital transducers 101 in different regions.

[0082] In this embodiment, in the step of using the mask layer 111 as a mask to remove the protective material layer 106 at the bottom of the mask opening 110, second interconnection windows 115 exposing at least part of the surface of the third electrode 105 are also formed in the protective material layer 106.

[0083] At least part of the surface of the third electrode 105 is exposed by the second interconnection windows 115, which facilitates subsequent electrical connection with the third electrode 105 through the pad, thereby realizing the output of the electrical signal of the interdigital transducer 101 through the third electrode 105.

[0084] In this embodiment, the process of removing the protective material layer 106 at the bottom of the mask opening 110 includes a dry etching process. The dry etching process has anisotropic etching characteristics, and the etching is more directional, which is beneficial to improving the topography and dimensional accuracy of the first interconnect window 114 and the second interconnect window 115. In other embodiments, a wet etching process may also be used to remove the protective material layer at the bottom of the mask opening.

[0085] Reference Figures 8 to 9 , a pad 116 is formed in the mask opening 110 (as Figure 9 shown), the pad 116 is also located in the interconnect window 112, the side wall of the pad 116 is aligned with the side wall of the interconnect window 112, and the pad 116 is electrically connected to the connection portion 102.

[0086] It should be noted that in the process of forming the pad 116, the protective material layer 106 at the bottom of the mask opening 110 is removed using the mask layer 111 as a mask, an interconnect window 112 is formed in the protective material layer 106, and then the pad 116 is formed in the mask opening 110. That is, in this embodiment, only one photomask is used to form the pad 116 and the interconnect window 112. Compared with the scheme of using two photomasks to form the pad and the interconnect window respectively, the number of photomasks is reduced, the production cost is correspondingly reduced, and moreover, the alignment accuracy between the interconnect window 112 and the pad 116 is improved, so that the side wall of the pad 116 is aligned with the side wall of the interconnect window 112, which is beneficial to improving the performance of the filter; in addition, since the protective material layer 106 is formed first and then the pad 116 is formed, the protective material layer 106 can protect the interdigital transducer 101, the connection portion 102 and the substrate 100, which is beneficial to reducing the probability of damage to the interdigital transducer 101, the connection portion 102 or the substrate 100 in the subsequent manufacturing process, and thus improves the performance of the filter.

[0087] In this embodiment, the step of forming the pad 116 in the mask opening 110 includes: Reference Figure 8 , a pad material layer 117 is formed in the mask opening 110, and the pad material layer 117 also covers the mask layer 111; Reference Figure 9 , the mask layer 111 and the pad material layer 117 on the top of the mask layer 111 are removed, and the remaining pad material layer 117 serves as the pad 116.

[0088] The pad material layer 117 is used to form the pad 116.

[0089] In this embodiment, the process of removing the mask layer 111 and the pad material layer 117 located on top of the mask layer 111 includes a lift-off process. Since the lift-off process omits the steps of the etching process, on the one hand, it is beneficial to reduce the production time and improve the production efficiency; on the other hand, it is easy to avoid the pattern distortion problem that occurs during the etching process, thereby improving the quality of the formed pad 116.

[0090] In this embodiment, in the step of forming the pad 116 in the mask opening 110, the pad 116 includes a first pad 118, the first pad 118 straddles the first electrode 103, and is electrically connected to the second electrodes 104 on both sides of the first electrode 103 through a first interconnect window 114 exposing the second electrode 104.

[0091] The first pad 118 is used to realize the electrical connection between the interdigital transducers 101 in different regions.

[0092] In this embodiment, the dielectric layer 109 is located between the first pad 118 and the protective layer 113.

[0093] It should be noted that since the dielectric layer 109 has a certain thickness, it is beneficial for the first pad 118 and the connection portion 102 to have a specific dielectric constant, thereby reducing the probability of generating parasitic capacitance between the first pad 118 and the connection portion 102.

[0094] In this embodiment, in the step of forming the pad 116 in the mask opening 110, the pad 116 further includes a second pad 119, and the second pad 119 is electrically connected to the third electrode 105 through a second interconnect window 115 exposing the third electrode 105.

[0095] The second pad 119 is used to output or input the electrical signal of the interdigital transducer 101 through the third electrode 105.

[0096] Figures 10 to 18 It is a schematic structural diagram corresponding to each step in the second embodiment of the formation method of the filter of the present invention. Specifically, Figure 18 is Figure 17 a partial enlarged view of area A.

[0097] The same parts of this embodiment and the first embodiment will not be described in detail here. The difference between this embodiment and the first embodiment is that: the substrate is a piezoelectric substrate on insulator.

[0098] In this embodiment, refer to Figure 10, in the step of providing the substrate 200, the substrate 200 includes a chip region I' and a peripheral region II' surrounding the chip region I', and both the interdigital transducer 201 and the connection portion 202 are located in the chip region I'.

[0099] The chip region I' refers to the device working area, and the peripheral region II' refers to the interconnect (bump) area for external power supply.

[0100] The substrate 200 is a piezoelectric-on-insulator substrate, and the substrate 200 includes a piezoelectric material layer, a low acoustic velocity layer, a high acoustic velocity layer, and a high-resistance silicon substrate stacked in sequence from top to bottom. Among them, the material of the piezoelectric material layer includes lithium tantalate or lithium niobate, the material of the low acoustic velocity layer includes silicon oxide, glass, silicon oxynitride, or tantalum oxide, and the material of the high acoustic velocity layer includes polysilicon, silicon nitride, aluminum oxide, aluminum nitride, or silicon carbide, etc. In this embodiment, the material of the piezoelectric material layer is lithium tantalate, the material of the low acoustic velocity layer is silicon oxide, and the material of the high acoustic velocity layer is polysilicon.

[0101] In this embodiment, an interdigital transducer 201 and a connection portion 202 are formed on the substrate 200. For a detailed description of the substrate 200, the interdigital transducer 201, and the connection portion 202, please refer to the relevant content of the first embodiment, which will not be elaborated here.

[0102] Reference Figures 11 to 12 , a protective material layer 206 (as Figure 12 shown) is formed on the substrate 200, and the protective material layer 206 covers the interdigital transducer 201, the connection portion 202, and the substrate 200.

[0103] Reference Figure 11 , in the step of forming the protective material layer 206, the protective material layer 206 at least includes a frequency modulation layer 207.

[0104] The frequency modulation layer 207 is used to adjust the operating frequency of the interdigital transducer 201. Specifically, by changing the thickness of the frequency modulation layer 207, the operating frequency of the interdigital transducer 201 can be adjusted.

[0105] In this embodiment, in the step of forming the protective material layer 206 on the substrate 200, the material of the frequency modulation layer 207 includes silicon oxide.

[0106] It should be noted that silicon oxide has relatively stable physical and chemical properties. In subsequent process manufacturing, silicon oxide is not easily removed and can play an effective protective role.

[0107] Reference Figure 12, in the step of forming the protective material layer 206, the protective material layer 206 further includes a passivation layer 208, and the frequency modulation layer 207 is located on top of the passivation layer 208.

[0108] The passivation layer 208 is used to protect the interdigital transducer 201, the connection part 202, and the substrate 200, thereby facilitating reducing the probability of damage to the interdigital transducer 201, the connection part 202, or the substrate 200 during subsequent manufacturing processes, and thus improving the performance of the filter.

[0109] In this embodiment, in the step of forming the protective material layer 206 on the substrate 200, the material of the passivation layer 208 includes silicon nitride or silicon oxynitride.

[0110] It should be noted that silicon nitride and silicon oxynitride have relatively stable physical and chemical properties, and are not easily removed during subsequent manufacturing processes, and can play an effective protective role.

[0111] In this embodiment, when the protective material layer 206 includes a stack of the passivation layer 208 and the frequency modulation layer 207, the frequency modulation layer 207 is located on top of the passivation layer 208. Therefore, before forming the frequency modulation layer 207, the passivation layer 208 can protect the substrate 200, the interdigital transducer 201, and the connection part 202, thereby further reducing the probability of damage to the substrate 200, the interdigital transducer 201, and the connection part 202.

[0112] In this embodiment, the step of forming the protective material layer 206 on the substrate 200 includes: Refer to Figure 11 , forming a passivation layer 208 on the substrate 200, and the passivation layer 208 covers the interdigital transducer 201, the connection part 202, and the substrate 200; Refer to Figure 12 , forming a frequency modulation layer 207 on the passivation layer 208, and the frequency modulation layer 207 and the passivation layer 208 constitute the protective material layer 206.

[0113] In this embodiment, the thickness of the frequency modulation layer 207 should not be too large or too small. If the thickness of the frequency modulation layer 207 is too large or too small, it is likely to affect the frequency adjustment effect of the frequency modulation layer 207 on the operating frequency of the interdigital transducer 201, and correspondingly, it is likely that the operating frequency of the frequency-modulated interdigital transducer 201 still does not meet the actual design requirements. Therefore, in this embodiment, the thickness of the frequency modulation layer 207 is 20 angstroms to 1000 angstroms.

[0114] In this embodiment, the thickness of the passivation layer 208 should not be too large or too small. If the thickness of the passivation layer 208 is too large, it is easy to increase the process time during the subsequent process of forming the interconnect window in the protective material layer 206, thereby reducing the working efficiency and affecting the product performance (such as the working frequency and insertion loss). If the thickness of the passivation layer 208 is too small, it is easy to cause poor protection effect of the passivation layer 208 on the interdigital transducer 201, the connecting portion 202, and the substrate 200. Therefore, in this embodiment, the thickness of the passivation layer 208 is 30 angstroms to 200 angstroms.

[0115] Reference Figure 13 , after forming the protective material layer 206 on the substrate 200 and before forming the dielectric layer on the protective material layer 206, it further includes: removing the protective material layer 206 in the peripheral region II' and a part of the thickness of the substrate 200, and retaining the protective material layer 206 in the chip region I'.

[0116] It should be noted that since the substrate 200 in this embodiment is a piezoelectric substrate on insulator and the piezoelectric material layer is relatively thin, therefore, after forming the protective material layer 206 on the substrate 200, first removing the protective material layer 206 in the peripheral region II' and a part of the thickness of the substrate 200 is beneficial to reducing the probability of damage to the piezoelectric material layer in the subsequent process and is also beneficial to improving the performance of the filter.

[0117] Specifically, the substrate 200 includes a piezoelectric material layer, a low sound velocity layer, a high sound velocity layer, and a high-resistance silicon substrate stacked in sequence from top to bottom. Therefore, in the step of removing a part of the thickness of the substrate 200 in the peripheral region II', at least the piezoelectric material layer in the peripheral region II' is removed. In a specific embodiment, the piezoelectric material layer, the low sound velocity layer, and the high sound velocity layer in the peripheral region II' are removed.

[0118] Reference Figure 14 , after removing the protective material layer 206 in the peripheral region II' and a part of the thickness of the substrate 200, a dielectric layer 209 is formed on the protective material layer 206. The dielectric layer 209 exposes the protective material layer 206 on a part of the surface of the connecting portion 202, and the dielectric layer 209 is used for electrically isolating the connecting portion 202 from the pad.

[0119] In this embodiment, in the step of forming the dielectric layer 209, the dielectric layer 209 is also located on the substrate 200 in the peripheral region II'.

[0120] The material of the dielectric layer 209 includes one or more of polyimide, silicon oxide, silicon nitride, aluminum oxide, and aluminum nitride. As an example, the material of the dielectric layer 209 is polyimide.

[0121] In this embodiment, since the connecting portion 202 includes a first electrode (not labeled) and second electrodes (not labeled) on both sides of the first electrode, the dielectric layer 209 extends across and covers the protective material layer 206 on the first electrode, and at least a part of the surface of the protective material layer 206 on the second electrode is exposed.

[0122] It should be noted that since the process of forming the dielectric layer 209 uses a spin coating process and the dielectric layer 209 is formed after removing the protective material layer 206 in the peripheral region II' and a part of the thickness of the substrate 200, the dielectric layer 209 is also located on the substrate 200 in the peripheral region II'.

[0123] Reference Figure 15 , after forming the dielectric layer 209 on the protective material layer 206, a mask layer 211 with a mask opening 210 is formed on the protective material layer 206, and the projection of the mask opening 210 on the connecting portion 202 covers a part of the surface of the connecting portion 202.

[0124] For a detailed description of the mask opening 210 and the mask layer 211, please refer to the relevant content of the first embodiment and will not be elaborated here.

[0125] Reference Figure 16 , using the mask layer 211 as a mask to remove the protective material layer 206 at the bottom of the mask opening 210, an interconnection window 212 is formed in the protective material layer 206, and the remaining protective material layer 206 serves as a protective layer 213.

[0126] For a detailed description of the interconnection window 212 and the protective layer 213, please refer to the relevant content of the first embodiment and will not be elaborated here.

[0127] Reference Figures 17 to 18 , a pad 216 is formed in the mask opening 210. The pad 216 is also located in the interconnection window 212. The sidewall of the pad 216 is aligned with the sidewall of the interconnection window 212, and the pad 216 is electrically connected to the connecting portion 202.

[0128] For a detailed description of the pad 216 and its forming method, please refer to the relevant content of the first embodiment and will not be elaborated here.

[0129] Correspondingly, the present invention also provides a semiconductor structure. Figure 19 It is a schematic structural diagram of the first embodiment of the filter of the present invention.

[0130] Reference Figure 19, the filter includes: a substrate 300; an interdigital transducer 301 located on the substrate 300; a connection portion 302 located on the substrate 300 at the side of the interdigital transducer 301, the connection portion 302 being electrically connected to the interdigital transducer 301; a protective layer 303 covering the interdigital transducer 301, the connection portion 302 and the substrate 300, the protective layer 303 having an interconnection window 304, the interconnection window 304 exposing a partial surface of the connection portion 302; a pad 305 located in the interconnection window 304, a side wall of the pad 305 being aligned with a side wall of the interconnection window 304, and the pad 305 being electrically connected to the connection portion 302.

[0131] The substrate 300 is used to provide a process platform for forming a surface acoustic wave filter. A SAW filter is a dedicated filtering device made using the piezoelectric effect and the physical properties of surface acoustic wave propagation. In a SAW filter, a signal undergoes two conversions of electric-acoustic-electric, thereby achieving the frequency selection characteristic. SAW filters have the advantages of high operating frequency, simple manufacturing process, low manufacturing cost, high consistency of frequency characteristics, etc. Therefore, they are widely used in various electronic devices.

[0132] In this embodiment, the substrate 300 is a piezoelectric substrate, so that the subsequent surface acoustic wave filter structure can perform filtering processing using the piezoelectric effect.

[0133] The material of the substrate 300 includes lithium niobate, lithium tantalate, quartz or piezoelectric ceramics. As an example, the material of the substrate 300 is lithium tantalate.

[0134] In other embodiments, the substrate can also be a piezoelectric-on-insulator substrate, and the substrate includes a piezoelectric material layer, a low acoustic velocity layer, a high acoustic velocity layer, and a high-resistance silicon substrate stacked in sequence from top to bottom. Among them, the material of the piezoelectric material layer includes lithium tantalate or lithium niobate, the material of the low acoustic velocity layer includes silicon oxide, glass, silicon oxynitride or tantalum oxide, and the material of the high acoustic velocity layer includes polysilicon, silicon nitride, aluminum oxide, aluminum nitride or silicon carbide, etc. As an example, the material of the piezoelectric material layer is lithium tantalate, the material of the low acoustic velocity layer is silicon oxide, and the material of the high acoustic velocity layer is polysilicon.

[0135] The interdigital transducer 301 is used to achieve the mutual conversion between electric signals and acoustic signals, so that the surface acoustic wave filter can perform filtering processing on signals. In this embodiment, the formed filter is a SAW filter. Therefore, the interdigital transducer 301 is correspondingly an interdigital electrode structure, and the interdigital transducer 301 includes a plurality of electrode fingers. Specifically, the interdigital transducer 301 is a metal interdigital transducer.

[0136] The material of the interdigital transducer 301 includes one or more of Mo, Al, Pt, W, Au, Al, Cr, Cu, Ni, and Ag. In this embodiment, the material of the interdigital transducer 301 is aluminum. Specifically, a metal film is deposited on the substrate 300, and the metal film is patterned through photolithography and etching processes to form the interdigital transducer 301.

[0137] The connecting portion 302 is used to realize the electrical connection between the interdigital transducer 301 and the pad 305, so as to realize the electrical connection between the interdigital transducer 301 and the external circuit structure. Alternatively, the connecting portion 302 can also be used to realize the electrical connection between the interdigital transducers 301 in different regions.

[0138] In this embodiment, the connecting portion 302 and the interdigital transducer 301 are formed in the same step, which is beneficial to reducing the process steps and the process cost. Therefore, in this embodiment, the material of the connecting portion 302 is the same as that of the interdigital transducer 301.

[0139] In this embodiment, the connecting portion 302 includes a first electrode 306 and second electrodes 307 located on both sides of the first electrode 306, and the first electrode 306 and the second electrodes 307 are respectively electrically connected to at least one of the interdigital transducers 301.

[0140] The second electrode 307 is used to realize the electrical connection between the interdigital transducers 301 in different regions.

[0141] Specifically, the connecting portion 302 that realizes electrical connection with other connecting portions 302 through the pad 305 serves as the second electrode 307.

[0142] The connecting portion 302 located between the adjacent and spaced second electrodes 307 serves as the first electrode 306.

[0143] The first electrode 306 is used to realize the electrical connection between the interdigital transducers 301 in different regions; or, the first electrode 306 is used to be electrically connected to one interdigital transducer 301.

[0144] In this embodiment, the surface acoustic wave filter is a longitudinal coupled dual-mode resonator type filter. The DMS filter utilizes the dual-mode characteristics of the surface acoustic wave, and the stopband suppression and bandwidth indexes of the filter are flexibly designed by adding a reflector between two interdigital transducers. Due to its structural characteristics, the DMS filter can provide performance similar to that of a bulk acoustic wave filter at low frequencies with less loss; in addition, in the design of the DMS filter, by changing the key parameters of the circuit topology and introducing new transmission zeros, the out-of-band suppression characteristics in the high-frequency band can be improved. Therefore, it is widely used in various electronic devices.

[0145] In other embodiments, according to actual design requirements, the type of the surface acoustic wave filter may also be other types of filters.

[0146] In this embodiment, the connecting portion 302 further includes a third electrode 312, and the third electrode 312 is electrically connected to at least one of the interdigital transducers 301.

[0147] The third electrode 312 is used as the input end or the output end of the interdigital transducer 301.

[0148] The protective layer 303 is used to protect the interdigital transducer 301, the connecting portion 302 and the substrate 300.

[0149] In this embodiment, since the protective layer 303 covers the interdigital transducer 301, the connecting portion 302 and the substrate 300, the protective layer 303 can protect the interdigital transducer 301, the connecting portion 302 and the substrate 300, which is beneficial to reducing the probability of damage to the interdigital transducer 301, the connecting portion 302 or the substrate 300 during the manufacturing process, and thus improves the performance of the filter.

[0150] The protective layer 303 at least includes a frequency modulation layer 309.

[0151] In this embodiment, the protective layer 303 is a single layer.

[0152] Specifically, the protective layer 303 is the frequency modulation layer 309.

[0153] The frequency modulation layer 309 can not only be used to protect the interdigital transducer 301, the connecting portion 302 and the substrate 300 in subsequent processes, but also be used to adjust the operating frequency of the interdigital transducer 301. Specifically, the operating frequency of the interdigital transducer 301 can be adjusted by changing the thickness of the frequency modulation layer 309.

[0154] In other embodiments, the protective material layer may be a laminate.

[0155] In this embodiment, the thickness of the frequency modulation layer 309 should not be too large or too small. If the thickness of the frequency modulation layer 309 is too large or too small, it is likely to affect the adjustment effect of the frequency modulation layer 309 on the operating frequency of the interdigital transducer 301, and correspondingly, it is likely to cause the operating frequency of the frequency-modulated interdigital transducer 301 to still not meet the actual design requirements. Therefore, in this embodiment, the thickness of the frequency modulation layer 309 is 20 angstroms to 1000 angstroms.

[0156] In this embodiment, the material of the frequency modulation layer 309 includes silicon oxide.

[0157] It should be noted that silicon oxide has relatively stable physical and chemical properties and is not easily removed in subsequent process steps, which can play an effective protective role.

[0158] In this embodiment, the interconnect window 304 includes first interconnect windows 310 located on both sides of the first electrode 306, and the first interconnect windows 310 expose at least a part of the surface of the second electrode 307.

[0159] The interconnect window 304 provides a spatial position for achieving electrical connection between the pad 305 and the connection portion 302.

[0160] The first interconnect windows 310 expose at least a part of the surface of the second electrode 307, facilitating electrical connection of the second electrodes 307 on both sides of the first electrode 306 through the pad 305, thereby achieving electrical connection between the interdigital transducers 301 in different regions.

[0161] In this embodiment, the interconnect window 304 further includes second interconnect windows 311 that expose at least a part of the surface of the third electrode 312.

[0162] The second interconnect windows 311 expose at least a part of the surface of the third electrode 312, facilitating electrical connection with the third electrode 312 through the pad 305, thereby achieving output of the electrical signal of the interdigital transducer 301 through the third electrode 312.

[0163] The pad 305 is used to achieve electrical connection with the connection portion 302.

[0164] It should be noted that since the sidewall of the pad 305 is aligned with the sidewall of the interconnect window 304, and the interconnect window 304 is located in the protective layer 303, that is, only one photomask is used in this embodiment to form the pad 305 and the interconnect window 304. Compared with the solution of using two photomasks to form the pad and the interconnect window respectively, the number of photomasks is reduced, the production cost is correspondingly reduced, and moreover, the alignment accuracy between the interconnect window 304 and the pad 305 is improved, which is beneficial to improving the performance of the filter.

[0165] In this embodiment, the pad 305 includes a first pad 313, the first pad 313 straddles the first electrode 306, and is electrically connected to the second electrodes 307 on both sides of the first electrode 306 via the first interconnect windows 310 that expose the second electrode 307.

[0166] The first pad 313 is used to achieve electrical connection between the interdigital transducers 301 in different regions.

[0167] In this embodiment, the pad 305 further includes a second pad 314, and the second pad 314 is electrically connected to the third electrode 312 through a second interconnection window 311 exposing the third electrode 312.

[0168] The second pad 314 is used to output or input the electrical signal of the interdigital transducer 301 through the third electrode 312.

[0169] In this embodiment, the filter further includes: a dielectric layer 315, located between the protective layer 303 and the pad 305.

[0170] The dielectric layer 315 has insulating properties, which is beneficial to improving the electrical isolation effect between the connection portion 302 covered by it and the pad 305.

[0171] The material of the dielectric layer 315 includes one or more of polyimide, silicon oxide, silicon nitride, aluminum oxide, and aluminum nitride. Polyimide, silicon oxide, silicon nitride, aluminum oxide, and aluminum nitride all have good insulating properties. As an example, the material of the dielectric layer 315 is polyimide.

[0172] In this embodiment, the dielectric layer 315 spans and covers the protective layer 303 located on the first electrode 306 and exposes at least a part of the surface of the second electrode 307.

[0173] It should be noted that the dielectric layer 315 spanning and covering the protective layer 303 located on the first electrode 306 is beneficial to improving the electrical isolation effect between the first electrode 306 and the pad 305.

[0174] In this embodiment, the dielectric layer 315 is located between the first pad 313 and the protective layer 303.

[0175] It should be noted that since the dielectric layer 315 has a certain thickness, it is beneficial for the first pad 313 and the connection portion 302 to have a specific dielectric constant, thereby reducing the probability of generating parasitic capacitance between the first pad 313 and the connection portion 302. As an example, the thickness of the dielectric layer 315 is 1.8 micrometers to 3 micrometers.

[0176] Figure 20 It is a schematic structural diagram of the second embodiment of the filter of the present invention.

[0177] The same parts of this embodiment and the foregoing embodiments will not be described in detail here. The differences between this embodiment and the foregoing embodiments are that: the substrate is a piezoelectric substrate on insulator.

[0178] In this embodiment, the substrate 500 includes a chip region i and a peripheral region ii surrounding the chip region i, and the top of the substrate 500 in the peripheral region ii is lower than the top of the substrate 500 in the chip region i.

[0179] The chip area i refers to the device working area, and the peripheral area ii refers to the interconnection area for external power supply.

[0180] Correspondingly, the interdigital transducer 501, the connection part 502, and the protective layer 503 are all located in the chip area i.

[0181] The substrate 500 is a piezoelectric-on-insulator substrate, and the substrate 500 includes a piezoelectric material layer, a low acoustic velocity layer, a high acoustic velocity layer, and a high-resistance silicon substrate stacked in sequence from top to bottom. Among them, the material of the piezoelectric material layer includes lithium tantalate or lithium niobate, the material of the low acoustic velocity layer includes silicon oxide, glass, silicon oxynitride, or tantalum oxide, and the material of the high acoustic velocity layer includes polysilicon, silicon nitride, aluminum oxide, aluminum nitride, or silicon carbide, etc. In this embodiment, the material of the piezoelectric material layer is lithium tantalate, the material of the low acoustic velocity layer is silicon oxide, and the material of the high acoustic velocity layer is polysilicon.

[0182] It should be noted that since the substrate 500 in this embodiment is a piezoelectric-on-insulator substrate and the piezoelectric material layer is relatively thin, the top of the substrate 500 in the peripheral area ii is lower than the top of the substrate 500 in the chip area i, that is, there is no piezoelectric material layer in the peripheral area ii, which is beneficial to reducing the probability of damage to the piezoelectric material layer in subsequent process fabrication and is also beneficial to improving the performance of the filter.

[0183] Specifically, in this embodiment, the substrate 500 in the chip area i includes a piezoelectric material layer, a low acoustic velocity layer, a high acoustic velocity layer, and a high-resistance silicon substrate stacked in sequence from top to bottom; the substrate 500 in the peripheral area ii is a high-resistance silicon substrate.

[0184] In this embodiment, the protective layer 503 at least includes a frequency modulation layer 509.

[0185] The frequency modulation layer 509 is used to adjust the operating frequency of the interdigital transducer 501. Specifically, by changing the thickness of the frequency modulation layer 509, the operating frequency of the interdigital transducer 501 can be adjusted.

[0186] In this embodiment, the protective layer 503 further includes a passivation layer 508, and the frequency modulation layer 509 is located on top of the passivation layer 508.

[0187] In this embodiment, the thickness of the frequency modulation layer 509 should not be too large or too small. If the thickness of the frequency modulation layer 509 is too large or too small, it is likely to affect the adjustment effect of the frequency modulation layer 509 on the operating frequency of the interdigital transducer 501, and correspondingly, it is likely that the operating frequency of the frequency-modulated interdigital transducer 501 still does not meet the actual design requirements. Therefore, in this embodiment, the thickness of the frequency modulation layer 509 is 20 angstroms to 1000 angstroms.

[0188] In this embodiment, the material of the frequency modulation layer 509 includes silicon oxide.

[0189] It should be noted that silicon oxide has relatively stable physical and chemical properties and is not easily removed in subsequent process steps, which can play an effective protective role.

[0190] The passivation layer 508 is used to protect the interdigital transducer 501, the connection part 502, and the substrate 500, which is beneficial to reducing the probability of damage to the interdigital transducer 501, the connection part 502, or the substrate 500 in subsequent process steps, thereby improving the performance of the filter.

[0191] In this embodiment, the frequency modulation layer 509 is located on top of the passivation layer 508. Therefore, before the formation of the frequency modulation layer 509, the passivation layer 508 can protect the substrate 500, the interdigital transducer 501, and the connection part 502, thereby further reducing the probability of damage to the substrate 500, the interdigital transducer 501, and the connection part 502.

[0192] In this embodiment, the thickness of the passivation layer 508 should neither be too large nor too small. If the thickness of the passivation layer 508 is too large, it is easy to increase the process time during the process of forming an interconnection window in the protective material layer (not shown in the figure), thereby reducing the working efficiency and affecting the product performance (such as the operating frequency and insertion loss). If the thickness of the passivation layer 508 is too small, it is easy to make the passivation layer 508 ineffective in protecting the interdigital transducer 501, the connection part 502, and the substrate 500. Therefore, in this embodiment, the thickness of the passivation layer 508 is 30 angstroms to 200 angstroms.

[0193] In this embodiment, the material of the passivation layer 508 includes silicon nitride or silicon oxynitride.

[0194] It should be noted that silicon nitride and silicon oxynitride have relatively stable physical and chemical properties and are not easily removed in subsequent process steps, which can play an effective protective role.

[0195] In this embodiment, the filter further includes: a dielectric layer 515, located between the protective layer 503 and the pad 505.

[0196] Specifically, the dielectric layer 515 is also located on the substrate 500 in the peripheral region ii.

[0197] The material of the dielectric layer 515 includes one or more of polyimide, silicon oxide, silicon nitride, aluminum oxide, and aluminum nitride. As an example, the material of the dielectric layer 515 is polyimide.

[0198] In this embodiment, since the connecting portion 502 includes a first electrode (not labeled) and second electrodes (not labeled) on both sides of the first electrode, the dielectric layer 515 spans and covers the protective layer 503 on the first electrode and exposes at least a part of the surface of the second electrode.

[0199] It should be noted that since the process for forming the dielectric layer 515 uses a spin coating process and the dielectric layer 515 is formed after removing the protective material layer (not shown in the figure) in the peripheral region ii and a part of the thickness of the substrate 500, the dielectric layer 515 is also located on the substrate 500 in the peripheral region ii.

[0200] For a specific description of the filter in this embodiment, reference can be made to the corresponding description in the foregoing embodiments, which will not be elaborated here.

[0201] The filter structure of the embodiment of the present invention can be formed by using the formation method of the filter structure in the foregoing embodiment, or can be formed by using other formation methods of the filter structure, which will not be elaborated here in this embodiment.

[0202] Correspondingly, the embodiment of the present invention further provides an electronic device, and the electronic device includes the filter according to any embodiment of the present invention.

[0203] The filter can be assembled into various electronic devices. As can be seen from the foregoing analysis, the performance of the filter is relatively high, and correspondingly, a high-performance electronic device can be obtained. Among them, the electronic device may further include a personal computer, a mobile terminal such as a smart phone, a media player, a navigation device, an electronic game device, a game controller, a tablet computer, a wearable device, an anti-access control electronic system, a POS terminal, a medical device, a flight simulator, etc.

[0204] 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 should be subject to the scope defined by the claims.

Claims

1. A method for forming a filter, characterized in that Comprising: Providing a substrate, on which an interdigital transducer and a connection part located at a side of the interdigital transducer are formed, the connection part being electrically connected to the interdigital transducer, the connection part including a first electrode and second electrodes located on both sides of the first electrode, the first electrode and the second electrodes being respectively electrically connected to at least one of the interdigital transducers; Forming a protective material layer on the substrate, the protective material layer covering the interdigital transducer, the connection part and the substrate; Forming a mask layer having a mask opening on the protective material layer, a projection of the mask opening on the connection part covering a partial surface of the connection part; Using the mask layer as a mask to remove the protective material layer at the bottom of the mask opening, forming an interconnection window in the protective material layer, and using the remaining protective material layer as a protective layer; Forming a pad in the mask opening of the mask layer, the pad also being located in the interconnection window, a side wall of the pad being aligned with a side wall of the interconnection window, and the pad being electrically connected to the connection part, the pad being formed on top of the connection part.

2. The method for forming a filter according to claim 1, wherein After forming the protective material layer on the substrate and before forming the mask layer having the mask opening on the protective material layer, further comprising: forming a dielectric layer on the protective material layer, the dielectric layer exposing the protective material layer on a partial surface located at the connection part; In the step of forming the mask layer having the mask opening on the protective material layer, the mask opening exposes at least a partial surface of the dielectric layer and a partial surface of the protective material layer exposed by the dielectric layer.

3. The method for forming a filter according to claim 2, wherein The material of the dielectric layer includes one or more of polyimide, silicon oxide, silicon nitride, aluminum oxide and aluminum nitride.

4. The method for forming a filter according to claim 2, characterized in that, In the step of forming the dielectric layer on the protective material layer, the dielectric layer transversely covers the protective material layer located on the first electrode and exposes at least a partial surface of the protective material layer located on the second electrode; In the step of forming the mask layer having the mask opening on the protective material layer, the mask opening transversely crosses the dielectric layer and exposes the dielectric layer on the first electrode and partial surfaces of the protective material layers on both sides of the first electrode; In the step of using the mask layer as a mask to remove the protective material layer at the bottom of the mask opening, forming a first interconnection window in the protective material layers on both sides of the first electrode, and the first interconnection window exposing at least a partial surface of the second electrode; In the step of forming the pad in the mask opening, the pad includes a first pad, the first pad transversely crossing the first electrode and being electrically connected to the second electrodes on both sides of the first electrode via the first interconnection window exposing the second electrode.

5. The method for forming a filter according to any one of claims 1 to 4, characterized in that The connection part further includes a third electrode, the third electrode being electrically connected to at least one of the interdigital transducers; In the step of using the mask layer as a mask to remove the protective material layer at the bottom of the mask opening, forming a second interconnection window in the protective material layer exposing at least a partial surface of the third electrode; In the step of forming a pad in the mask opening, the pad includes a second pad, and the second pad is electrically connected to the third electrode via a second interconnect window exposing the third electrode.

6. The method for forming a filter according to claim 2, wherein, In the step of providing the substrate, the substrate includes a chip region and a peripheral region surrounding the chip region, and both the interdigital transducer and the connection portion are located in the chip region; After forming the protective material layer on the substrate and before forming the mask dielectric layer on the protective material layer, it further includes: removing the protective material layer in the peripheral region and a part of the thickness of the substrate, and retaining the protective material layer located in the chip region; In the step of forming the dielectric layer, the dielectric layer is also located on the substrate in the peripheral region.

7. The method for forming a filter according to claim 1, wherein, The process of forming the protective material layer on the substrate includes a physical vapor deposition process.

8. The method for forming a filter according to claim 1, wherein, The process of removing the protective material layer at the bottom of the mask opening includes a dry etching process.

9. The method for forming a filter according to claim 1, wherein, The step of forming a pad in the mask opening includes: forming a pad material layer in the mask opening, and the pad material layer also covers the mask layer; Removing the mask layer and the pad material layer on top of the mask layer, and the remaining pad material layer serves as the pad.

10. The method for forming a filter according to claim 1, wherein, In the step of forming the protective material layer, the protective material layer at least includes a frequency modulation layer.

11. The method for forming a filter according to claim 10, characterized in that, In the step of forming the protective material layer, the protective material layer further includes a passivation layer, and the frequency modulation layer is located on top of the passivation layer.

12. The method for forming a filter according to claim 11, characterized in that, In the step of forming the protective material layer on the substrate, the material of the frequency modulation layer includes silicon oxide, and the material of the passivation layer includes silicon nitride or silicon oxynitride.

13. The method for forming the filter according to claim 1, characterized in that, The material of the mask layer includes photoresist.

14. A filter, characterized in that, Including: A substrate; An interdigital transducer located on the substrate; A connection portion located on the substrate at the side of the interdigital transducer, the connection portion electrically connects the interdigital transducer, the connection portion includes a first electrode and second electrodes located on both sides of the first electrode, and the first electrode and the second electrodes are respectively electrically connected to at least one of the interdigital transducers; A protective layer covering the interdigital transducer, the connection portion and the substrate, and there are interconnect windows in the protective layer, and the interconnect windows expose a part of the surface of the connection portion; A pad located in the interconnect window, the side wall of the pad is aligned with the side wall of the interconnect window, and the pad is electrically connected to the connection portion, and the pad is formed on top of the connection portion.

15. The filter according to claim 14, characterized in that, The filter further includes: a dielectric layer located between the protective layer and the pad.

16. The filter according to claim 15, characterized in that, The interconnect window includes first interconnect windows located on both sides of the first electrode, and the first interconnect windows expose at least a part of the surface of the second electrode; The pad includes a first pad, the first pad straddles the first electrode, and is electrically connected to the second electrodes on both sides of the first electrode via the first interconnect window exposing the second electrode; The dielectric layer is located between the first pad and the protective layer.

17. The filter according to any one of claims 14 to 16, characterized in that, The connection portion further includes a third electrode, and the third electrode is electrically connected to at least one of the interdigital transducers; The interconnect window further includes a second interconnect window exposing at least a part of the surface of the third electrode; The pad includes a second pad, and the second pad is electrically connected to the third electrode via a second interconnect window exposing the third electrode.

18. The filter according to claim 15, wherein The material of the dielectric layer includes one or more of polyimide, silicon oxide, silicon nitride, aluminum oxide, and aluminum nitride.

19. The filter according to claim 15, characterized in that, The substrate includes a chip region and a peripheral region surrounding the chip region, and the top of the substrate in the peripheral region is lower than the top of the substrate in the chip region; The interdigital transducer, the connecting portion, and the protective layer are all located in the chip region; The dielectric layer is also located on the substrate in the peripheral region.

20. The filter according to claim 14, characterized in that, The substrate includes a piezoelectric substrate or a piezoelectric-on-insulator substrate.

21. The filter according to claim 14, wherein The protective layer includes at least a frequency modulation layer.

22. The filter according to claim 21, wherein The protective layer further includes a passivation layer, and the frequency modulation layer is located on top of the passivation layer.

23. The filter according to claim 22, wherein, The thickness of the passivation layer is from 30 angstroms to 200 angstroms.

24. The filter according to claim 22, wherein The material of the frequency modulation layer includes silicon oxide, and the material of the passivation layer includes silicon nitride or silicon oxynitride.

25. The filter according to claim 21, characterized in that, The thickness of the frequency modulation layer is from 20 angstroms to 1000 angstroms.

26. An electronic device, characterized in that, Comprising a filter according to any one of claims 14 to 25.

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