Filter, forming method thereof and electronic equipment

Abstract

A filter, a method of forming the same, and an electronic device, the filter including: an acoustic transducer including a lead-out portion; the temperature compensation layer covers the acoustic transducer and the substrate, and at least part of the surface of the leading-out part is exposed; the first passivation layer covers the temperature compensation layer and exposes the lead-out part at the side part of the temperature compensation layer, and the surface of the lead-out part exposed by the first passivation layer is used as an interconnection region of the lead-out part; the bonding pad is positioned at the side part of the first passivation layer, covers the interconnection region of the lead-out part and is electrically connected with the lead-out part; the surface, exposed by the first passivation layer, of the lead-out part serves as an interconnection area of the lead-out part, namely the first passivation layer is further used for defining an area, connected with the bonding pad, of the lead-out part, so that the influence of the bonding pad forming process on the forming quality of the first passivation layer on the temperature compensation layer is avoided, the forming quality of the first passivation layer is high, and the service life of the temperature compensation layer is prolonged. Correspondingly, the protection effect of the first passivation layer on the temperature compensation layer is guaranteed, so that the problems of high acceleration temperature and humidity and bias voltage test failure of the filter are solved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing, and more particularly to a filter and a method for forming the same, as well as an electronic device. Background Technology

[0002] Radio frequency (RF) front-end chips in wireless communication devices include power amplifiers, antenna switches, RF filters, multiplexers, and low-noise amplifiers. Among these, RF filters include surface acoustic wave (SAW) filters, bulk acoustic wave (BAW) filters, micro-electro-mechanical system (MEMS) filters, and integrated passive device (IPD) filters.

[0003] SAW filters have a high quality factor (Q value) and are used to create radio frequency filters with low insertion loss and high out-of-band rejection. As one of the most widely used filters in current wireless communication devices, the high reliability of SAW filters can extend the lifespan of electronic devices and expand their application range.

[0004] Currently, the performance of SAW filters still needs improvement. Summary of the Invention

[0005] The problem solved by the embodiments of the present invention is to provide a filter and its formation method, as well as an electronic device, which is beneficial to improving the failure of the filter under high acceleration temperature and humidity and bias voltage tests.

[0006] To address the aforementioned problems, embodiments of the present invention provide a filter, comprising: a substrate; an acoustic transducer located on the substrate, the acoustic transducer including a lead-out portion; a temperature compensation layer covering the acoustic transducer and the substrate, wherein the temperature compensation layer exposes at least a portion of the surface of the lead-out portion; a first passivation layer covering the temperature compensation layer and exposing the lead-out portion on a side of the temperature compensation layer, wherein the surface of the lead-out portion exposed by the first passivation layer serves as an interconnection region of the lead-out portion; a pad located on a side of the first passivation layer and covering the interconnection region of the lead-out portion, the pad being electrically connected to the lead-out portion; and a second passivation layer covering the first passivation layer and the pad, wherein the second passivation layer exposes at least a portion of the surface of the pad.

[0007] Accordingly, embodiments of the present invention also provide an electronic device, including: the filter described in any embodiment of the present invention.

[0008] Accordingly, embodiments of the present invention also provide a method for forming a filter, comprising: providing a substrate on which an acoustic transducer is formed, the acoustic transducer including a lead-out portion; forming a temperature compensation layer on the substrate, the temperature compensation layer covering the acoustic transducer and exposing at least a portion of the surface of the lead-out portion; forming a first passivation layer having an interconnection window on the temperature compensation layer, the interconnection window exposing the lead-out portion on a side of the temperature compensation layer; forming a pad in the interconnection window, the pad being electrically connected to the lead-out portion; and forming a second passivation layer covering the first passivation layer and the pad, the second passivation layer exposing at least a portion of the surface of the pad.

[0009] Compared with the prior art, the technical solution of the embodiments of the present invention has the following advantages: This invention provides a filter, comprising: an acoustic transducer located on a substrate, the acoustic transducer including a lead-out portion; a temperature compensation layer covering the acoustic transducer and the substrate, wherein the temperature compensation layer exposes at least a portion of the surface of the lead-out portion; a first passivation layer covering the temperature compensation layer and exposing the lead-out portion on a side of the temperature compensation layer, the surface of the lead-out portion exposed by the first passivation layer serving as an interconnection region of the lead-out portion; a pad located on a side of the first passivation layer and covering the interconnection region of the lead-out portion, the pad being electrically connected to the lead-out portion; and a second passivation layer covering the first passivation layer and the substrate. The pads are exposed by the second passivation layer, with at least a portion of the pad surface exposed. In some embodiments, the lead surface exposed by the first passivation layer serves as the interconnection area of ​​the lead, i.e., the first passivation layer also defines the area where the lead connects to the pads, thereby avoiding the influence of the pad formation process on the formation quality of the first passivation layer on the temperature compensation layer, resulting in higher formation quality of the first passivation layer. Consequently, the protective effect of the first passivation layer on the temperature compensation layer is guaranteed, and the possibility of water vapor in the air entering the temperature compensation layer is reduced, thereby improving the problem of filter failure in high-accelerated temperature and humidity and Uhast test, and thus improving the performance of the filter.

[0010] This invention also provides a method for forming a filter, comprising: providing a substrate on which an acoustic transducer is formed, the acoustic transducer including a lead-out portion; forming a temperature compensation layer on the substrate, the temperature compensation layer covering the acoustic transducer and exposing at least a portion of the surface of the lead-out portion; forming a first passivation layer having an interconnection window on the temperature compensation layer, the interconnection window exposing the lead-out portion on the side of the temperature compensation layer; forming a pad in the interconnection window, the pad being electrically connected to the lead-out portion; forming a second passivation layer covering the first passivation layer and the pad, the second passivation layer exposing at least a portion of the surface of the pad; in some embodiments, the first passivation layer is formed on the temperature compensation layer first, and then the pad is formed, thereby avoiding the influence of the pad formation process on the formation quality of the first passivation layer on the temperature compensation layer, resulting in higher formation quality of the first passivation layer, thereby ensuring the protective effect of the first passivation layer on the temperature compensation layer, reducing the possibility of water vapor in the air entering the temperature compensation layer, thereby improving the problems of high acceleration temperature and humidity and bias voltage test failure of the filter, and thus improving the performance of the filter. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of a filter structure; Figures 2 to 3 This is a schematic diagram of the structure of an embodiment of the filter of the present invention; Figures 4 to 12 This is a schematic diagram of the structure corresponding to each step in one embodiment of the filter formation method of the present invention. Detailed Implementation

[0012] Currently, the performance of filters still needs improvement. This paper analyzes the reasons why the performance of filters needs further improvement, using a schematic diagram of one such filter as an example.

[0013] Figure 1 This is a schematic diagram of a filter structure.

[0014] refer to Figure 1 The filter includes: a substrate 10; an acoustic transducer 11 located on the substrate 10, the acoustic transducer 11 including a lead-out portion 12; a temperature compensation layer 13 covering the acoustic transducer 11 and the substrate 10, and the temperature compensation layer 13 exposing at least a portion of the surface of the lead-out portion 12, the surface of the lead-out portion 12 exposed by the temperature compensation layer 13 serving as an interconnection region i of the lead-out portion 12; a pad 14 covering the interconnection region i of the lead-out portion 12, the pad 14 being electrically connected to the lead-out portion 12; and a passivation layer 15 covering the temperature compensation layer 13 and the pad 14, the passivation layer 15 exposing at least a portion of the surface of the pad 14.

[0015] Research has revealed that the surface of the lead-out portion 12 exposed by the temperature compensation layer 13 serves as the interconnection area i of the lead-out portion 12. That is, the temperature compensation layer 13 also defines the area where the lead-out portion 12 connects to the pad 14. Furthermore, the passivation layer 15 covers both the temperature compensation layer 13 and the pad 14. As a result, the formation process of the pad 14 affects the formation quality of the passivation layer 15 on the temperature compensation layer 13, leading to poor formation quality of the passivation layer 15. Consequently, the protective effect of the passivation layer 15 on the temperature compensation layer 13 is reduced, increasing the possibility of water vapor in the air entering the temperature compensation layer 13. This increases the risk of filter failure during high-acceleration temperature and humidity tests and bias voltage tests, thereby reducing the filter's performance.

[0016] To address the aforementioned technical problems, embodiments of the present invention provide a filter, comprising: a substrate; an acoustic transducer located on the substrate, the acoustic transducer including a lead-out portion; a temperature compensation layer covering the acoustic transducer and the substrate, wherein the temperature compensation layer exposes at least a portion of the surface of the lead-out portion; a first passivation layer covering the temperature compensation layer and exposing the lead-out portion on a side of the temperature compensation layer, wherein the surface of the lead-out portion exposed by the first passivation layer serves as an interconnection region of the lead-out portion; a pad located on a side of the first passivation layer and covering the interconnection region of the lead-out portion, the pad being electrically connected to the lead-out portion; and a second passivation layer covering the first passivation layer and the pad, wherein the second passivation layer exposes at least a portion of the surface of the pad.

[0017] In the scheme disclosed in the embodiments of the present invention, the surface of the lead exposed by the first passivation layer serves as the interconnection area of ​​the lead. That is, the first passivation layer is also used to define the area where the lead connects to the pad, thereby avoiding the influence of the pad formation process on the formation quality of the first passivation layer on the temperature compensation layer, resulting in higher formation quality of the first passivation layer. Consequently, the protective effect of the first passivation layer on the temperature compensation layer is guaranteed, and the possibility of water vapor in the air entering the temperature compensation layer is reduced, thereby improving the problems of high acceleration temperature and humidity and bias voltage measurement failure of the filter, and thus improving the performance of the filter.

[0018] To make the above-mentioned objects, features and advantages of the embodiments of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0019] Figures 2 to 3 This is a schematic diagram of the structure of an embodiment of the filter of the present invention. Specifically, Figure 3 yes Figure 2 A magnified view of a portion at point A.

[0020] refer to Figures 2 to 3The filter includes: a substrate 100; an acoustic transducer 101 located on the substrate 100, the acoustic transducer 101 including a lead-out portion 102; a temperature compensation layer 103 covering the acoustic transducer 101 and the substrate 100, and the temperature compensation layer 103 exposing at least a portion of the surface of the lead-out portion 102; a first passivation layer 104 covering the temperature compensation layer 103 and exposing the side portion of the lead-out portion 102, the surface of the lead-out portion 102 exposed by the first passivation layer 104 serving as an interconnection region I of the lead-out portion 102; a pad 105 located on the side of the first passivation layer 104 and covering the interconnection region I of the lead-out portion 102, the pad 105 being electrically connected to the lead-out portion 102; and a second passivation layer 106 covering the first passivation layer 104 and the pad 105, the second passivation layer 106 exposing at least a portion of the surface of the pad 105.

[0021] Substrate 100 is used to provide a process platform for forming filters.

[0022] In some embodiments, a surface acoustic wave (SAW) filter is used as an example for illustration. A SAW filter is a specialized filtering device made using the piezoelectric effect and the physical characteristics of surface acoustic wave propagation. In a SAW filter, the signal undergoes two conversions: electro-acoustic and electro-acoustic, thereby achieving frequency selectivity. SAW filters have advantages such as high operating frequency, simple manufacturing process, low manufacturing cost, and high frequency response consistency; therefore, they are widely used in various electronic devices.

[0023] Accordingly, the substrate 100 is a piezoelectric substrate, thereby enabling the subsequent surface acoustic wave filter to utilize the piezoelectric effect for filtering.

[0024] The substrate 100 is made of materials including lithium niobate, lithium tantalate, quartz, or piezoelectric ceramics. As an example, the substrate 100 is made of lithium niobate.

[0025] The acoustic transducer 101 is used to convert between electrical signals and acoustic signals, thereby enabling the surface acoustic wave (SAW) filter to filter the signals. In some embodiments, the formed filter is a SAW filter; therefore, the acoustic transducer 101 is correspondingly an interdigital electrode 107, which includes the lead-out portion 102 and electrode fingers 108 located on the side of the lead-out portion 102, and the lead-out portion 102 is electrically connected to the electrode fingers 108. Specifically, the acoustic transducer 101 is a metal interdigital transducer (IDT).

[0026] It should be noted that the electrical connection between the lead-out portion 102 and the electrode finger 108 is not shown in the figure. In actual design, the lead-out portion 102 and the electrode finger 108 are electrically connected in other areas of the filter.

[0027] The lead-out section 102 is used to realize the electrical connection between the electrode finger 108 and the pad 105, thereby realizing the electrical connection between the acoustic transducer 101 and the external circuit structure.

[0028] The electrode fingers 108 and the lead-out portions 102 are made of one or more of molybdenum (Mo), aluminum (Al), platinum (Pt), tungsten (W), gold (Au), nickel (Ni), and silver (Ag). In some embodiments, the electrode fingers 108 and the lead-out portions 102 are both made of aluminum. Specifically, the electrode fingers 108 and the lead-out portions 102 are formed by depositing a metal film on a substrate 100 and patterning the metal film using photolithography and etching processes.

[0029] The temperature compensation layer 103 is used to offset the impact of temperature changes on the filter performance, ensuring that the filter maintains stable performance under different temperature environments.

[0030] In some embodiments, the temperature compensation layer 103 exposes at least a portion of the surface of the lead-out portion 102, which helps to reduce the difficulty of making an electrical connection between the pad 105 and the lead-out portion 102. As an example, the temperature compensation layer 103 exposes a portion of the surface of the lead-out portion 102.

[0031] The temperature compensation layer 103 includes a silicon oxide layer or a composite material layer with silicon oxide as the main component. As an example, the temperature compensation layer 103 is a silicon oxide layer.

[0032] It should be noted that, on the one hand, the silicon oxide layer or the composite material layer with silicon oxide as the main component has a frequency temperature coefficient opposite to that of the substrate 100. Therefore, when the temperature compensation layer 103 is combined with the substrate 100, it can effectively counteract the influence of temperature changes on the filter frequency, making the frequency temperature coefficient of the filter tend to zero, thereby ensuring that the filter can maintain stable performance under different temperature environments. On the other hand, the elastic modulus of the silicon oxide layer or the composite material layer with silicon oxide as the main component changes with temperature in the opposite direction to the elastic modulus of the substrate 100. Therefore, the silicon oxide layer or the composite material layer with silicon oxide as the main component can compensate for the stress changes of the substrate 100 caused by thermal expansion.

[0033] Specifically, a composite material layer with silicon dioxide as the main component refers to a composite material layer in which the silicon dioxide content is higher than the content of any other single material in the composite material layer.

[0034] The first passivation layer 104 serves not only to protect the temperature compensation layer 103 but also to adjust the operating frequency of the acoustic transducer 101. Specifically, the operating frequency of the acoustic transducer 101 can be adjusted by changing the thickness of the first passivation layer 104.

[0035] Specifically, the first passivation layer 104 has an interconnect window 109 that exposes the interconnect region I.

[0036] Therefore, the first passivation layer 104 can also be used to define the area where the lead-out portion 102 connects to the pad 105, that is, to define the interconnect region I. Specifically, the interconnect window 109 is used to provide space for the electrical connection between the pad 105 and the lead-out portion 102.

[0037] It should be noted that the surface of the lead-out portion 102 exposed by the first passivation layer 104 serves as the interconnection region I of the lead-out portion 102. That is, the first passivation layer 104 is also used to define the area where the lead-out portion 102 connects to the pad 105, thereby avoiding the influence of the formation process of the pad 105 on the formation quality of the first passivation layer 104 on the temperature compensation layer 103. This results in a higher formation quality of the first passivation layer 104, which in turn ensures the protective effect of the first passivation layer 104 on the temperature compensation layer 103. The possibility of water vapor in the air entering the temperature compensation layer 103 is reduced, thereby improving the problems of high acceleration temperature and humidity and bias voltage test failure of the filter, and thus improving the performance of the filter.

[0038] In some embodiments, the first passivation layer 104 includes one or two of the following: the first passivation layer 104 covers the top surface and sidewalls of the temperature compensation layer 103; the first passivation layer 104 covers a portion of the top surface of the temperature compensation layer 103 and exposes the sidewalls of the temperature compensation layer 103 adjacent to the interconnection region I, as well as a portion of the top surface connected to the exposed sidewalls.

[0039] It should be noted that the first passivation layer 104 covers the top surface and sidewall of the temperature compensation layer 103, that is, the first passivation layer 104 exposes part of the top surface of the lead-out portion 102 located on the side of the temperature compensation layer 103, and the corresponding pad 105 is located on part of the exposed top surface of the lead-out portion 102, so that the pad 105 can electrically connect the lead-out portion 102 with the adjacent electrode finger 108 to realize the series connection of the acoustic transducers 101; the first passivation layer 104 exposes the sidewall of the temperature compensation layer 103 adjacent to the interconnection region I, and part of the top surface connected to the exposed sidewall, that is, the pad 105 is located on the exposed sidewall of the temperature compensation layer 103 adjacent to the interconnection region I, and part of the top surface connected to the exposed sidewall, so the temperature compensation layer 103 isolates the pad 105 from the adjacent electrode finger 108 to realize the parallel connection of the acoustic transducers 101.

[0040] In some embodiments, at a local location on the substrate 100, the first passivation layer 104 covers the top surface and sidewalls of the temperature compensation layer 103, and at other locations on the substrate 100, the first passivation layer 104 covers a portion of the top surface of the temperature compensation layer 103, exposing the sidewalls of the temperature compensation layer 103 adjacent to the interconnection region I, and a portion of the top surface connected to the exposed sidewalls.

[0041] In some embodiments, at the location of the substrate, the first passivation layer covers the top surface and sidewalls of the temperature compensation layer; in other embodiments, at the location of the substrate, the first passivation layer covers a portion of the top surface of the temperature compensation layer and exposes the sidewalls of the temperature compensation layer adjacent to the interconnection region, as well as a portion of the top surface connected to the exposed sidewalls.

[0042] Accordingly, the interconnect window 109 in the first passivation layer 104 includes one or both of a first interconnect window 111 and a second interconnect window 112: the first interconnect window 111 exposes the sidewall of the temperature compensation layer 103 adjacent to the lead-out portion 102 and a portion of the top surface connected to the exposed sidewall; the second interconnect window 112 is located on the side of the temperature compensation layer 103 and exposes a portion of the top surface of the lead-out portion 102.

[0043] As an example, the interconnect window 109 in the first passivation layer 104 includes both a first interconnect window 111 and a second interconnect window 112.

[0044] In other embodiments, the interconnect window in the first passivation layer may include only the first interconnect window, or the interconnect window in the first passivation layer may include only the second interconnect window.

[0045] refer to Figure 3In some embodiments, a gap 110 is provided between the first passivation layer 104 and the pad 105.

[0046] It should be noted that during the formation of pad 105, a mask layer (not shown) with a mask opening (not shown) is formed on top of the first passivation layer 104. The angle between the sidewall of the mask opening and the top surface of the lead-out portion 102 is an acute angle. Therefore, the material of pad 105 is not easily formed on the mask layer, resulting in a gap between pad 105 and mask layer. At the same time, the mask layer covers the first passivation layer 104, and there is a gap 110 between the first passivation layer 104 and pad 105.

[0047] The thickness of the first passivation layer 104 should not be too small. If the thickness of the first passivation layer 104 is too small, it may result in poor protection of the temperature compensation layer 103, thereby increasing the possibility of water vapor in the air entering the temperature compensation layer 103. Therefore, in some embodiments, the thickness of the first passivation layer 104 is greater than or equal to 80 angstroms. Specifically, the thickness of the first passivation layer 104 can be 80 angstroms or 500 angstroms.

[0048] In some embodiments, the first passivation layer 104 includes one or more layers selected from silicon nitride, aluminum oxide, silicon carbide, silicon carbide, aluminum nitride, gallium arsenide, and gallium nitride. As an example, the first passivation layer 104 is a silicon nitride layer.

[0049] Specifically, the silicon nitride layer, aluminum oxide layer, silicon carbide layer, silicon carbide layer, aluminum nitride layer, gallium arsenide layer, and gallium nitride layer all have dense crystal structures, which can form a continuous and pore-free thin film. Therefore, they can effectively protect the layer and reduce the possibility of water vapor in the air entering the temperature compensation layer 103.

[0050] The pad 105 is used for the electrical connection lead-out section 102 to connect the electrical connection lead-out section 102 to the external circuit.

[0051] In some embodiments, the pad 105 is located on the side of the first passivation layer 104 and covers the interconnect region I of the lead-out portion 102. Specifically, the pad 105 is located in the interconnect window 109 in the first passivation layer 104.

[0052] It should be noted that, since the interconnect window 109 in the first passivation layer 104 includes one or both of the first interconnect window 111 and the second interconnect window 112, the corresponding pad 105 includes one or both of the first pad 113 and the second pad 114: the first pad 113 is located in the first interconnect window 111, that is, the first pad 113 covers the sidewall of the temperature compensation layer 103 adjacent to the lead-out portion 102 and the part of the top surface connected to the exposed sidewall; the second pad 114 is located in the second interconnect window 112, that is, the second pad 114 is located on the side of the temperature compensation layer 103 and covers part of the top surface of the lead-out portion 102.

[0053] Specifically, the first pad 113 covers the sidewall of the temperature compensation layer 103 adjacent to the lead-out portion 102 and the top surface connected to the exposed sidewall. Therefore, the temperature compensation layer 103 isolates the pad 105 from the adjacent electrode finger 108, realizing the parallel connection of the acoustic transducer 101.

[0054] The second pad 114 is used to make the lead-out part 102 electrically connected to the adjacent electrode finger 108, so as to realize the series connection of the acoustic transducer 101.

[0055] In some embodiments, the material of pad 105 includes one or more of aluminum, copper, gold, titanium, nickel, silver, and tungsten. It should be noted that aluminum, copper, gold, titanium, nickel, silver, and tungsten all have good electrical conductivity. As an example, the material of pad 105 is aluminum.

[0056] As an example, the pads include both a first pad 113 and a second pad 114.

[0057] In other embodiments, the pad may include only the first pad, or the pad may include only the second pad.

[0058] The second passivation layer 106 protects the first passivation layer 104 and the pads 105, helping to prevent them from being exposed to air. This reduces the probability of water vapor and pollutants in the air adhering to the first passivation layer 104 and the pads 105. It also helps to adjust the operating frequency of the acoustic transducer 101. Specifically, the operating frequency of the acoustic transducer 101 can be adjusted by changing the thickness of the second passivation layer 106.

[0059] In some embodiments, a gap 110 is provided between the first passivation layer 104 and the pad 105.

[0060] Therefore, refer to Figure 3In some embodiments, the second passivation layer 106 also fills the gap 110, thereby reducing the likelihood that water vapor in the air will enter the temperature compensation layer 103 through the gap 110.

[0061] In some embodiments, the density of the first passivation layer 104 is greater than that of the second passivation layer 106. Because the density of the first passivation layer 104 is greater, the first passivation layer 104 can protect the temperature compensation layer 103, thereby reducing the possibility that water vapor in the air will enter the temperature compensation layer 103 through the first passivation layer 104.

[0062] In some embodiments, the second passivation layer 106 includes one or more layers selected from silicon nitride, silicon oxide, aluminum oxide, silicon carbide, silicon carbide, aluminum nitride, gallium arsenide, and gallium nitride. As an example, the second passivation layer 106 is a silicon nitride layer.

[0063] The silicon nitride layer, silicon oxide layer, aluminum oxide layer, silicon carbide layer, silicon carbide layer, aluminum nitride layer, gallium arsenide layer, and gallium nitride layer all have a dense crystal structure and can form a continuous and pore-free thin film. Therefore, they can effectively protect the layer and reduce the possibility of water vapor in the air entering the temperature compensation layer 103.

[0064] The thickness of the second passivation layer 106 should not be too small. If the thickness of the second passivation layer 106 is too small, the thickness of the second passivation layer 106 filling the gap 110 will also be too small, thereby increasing the possibility that water vapor in the air will enter the temperature compensation layer 103 through the gap 110, which in turn increases the risk of filter failure during high-acceleration temperature and humidity and bias voltage tests. Therefore, in some embodiments, the thickness of the second passivation layer 106 is greater than or equal to 150 angstroms. Specifically, the thickness of the second passivation layer 106 can be 150 angstroms, 300 angstroms, or 1000 angstroms.

[0065] In some embodiments, the second passivation layer 106 exposes at least a portion of the surface of the pad 105, facilitating connection between the pad 105 and external circuitry.

[0066] As an example, the second passivation layer 106 exposes a portion of the surface of the pad 105.

[0067] In other embodiments, depending on actual design requirements, the structure of the filter of the present invention can also be applied to other types of filters that require a temperature compensation layer to be covered on the acoustic transducer.

[0068] Accordingly, embodiments of the present invention also provide an electronic device, which includes the filter described in any embodiment of the present invention.

[0069] Filters can be integrated into various electronic devices. As the foregoing analysis shows, filters offer high performance, which in turn enables high-performance electronic devices. These electronic devices can include personal computers, smartphones and other mobile terminals, media players, navigation devices, video game consoles, game controllers, tablet computers, wearable devices, security access control systems, POS terminals, medical devices, flight simulators, and more.

[0070] Accordingly, the present invention also provides a method for forming a filter. Figures 4 to 12 This is a schematic diagram of the structure corresponding to each step in one embodiment of the filter formation method of the present invention. Specifically, Figure 10 yes Figure 9 A magnified view of the area at point B. Figure 12 yes Figure 11 A magnified view of a section at point C.

[0071] refer to Figure 4 A substrate 500 is provided, on which an acoustic transducer 501 is formed, the acoustic transducer 501 including an outlet portion 502.

[0072] The substrate 500 is used to provide a process platform for forming filters.

[0073] In some embodiments, a surface acoustic wave (SAW) filter is used as an example for illustration. A SAW filter is a specialized filtering device made using the piezoelectric effect and the physical characteristics of surface acoustic wave propagation. In a SAW filter, the signal undergoes two conversions: electro-acoustic and electro-acoustic, thereby achieving frequency selectivity. SAW filters have advantages such as high operating frequency, simple manufacturing process, low manufacturing cost, and high frequency response consistency; therefore, they are widely used in various electronic devices.

[0074] Accordingly, the substrate 500 is a piezoelectric substrate, thereby enabling the subsequent surface acoustic wave filter structure to utilize the piezoelectric effect for filtering.

[0075] The substrate 500 is made of materials including lithium niobate, lithium tantalate, quartz, or piezoelectric ceramics. As an example, the substrate 500 is made of lithium niobate.

[0076] The acoustic transducer 501 is used to convert between electrical signals and acoustic signals, thereby enabling the surface acoustic wave (SAW) filter to filter the signals. In some embodiments, the formed filter is a SAW filter; therefore, the acoustic transducer 501 is correspondingly an interdigital electrode 507, which includes the lead-out portion 502 and electrode fingers 508 located on the side of the lead-out portion 502, and the lead-out portion 502 is electrically connected to the electrode fingers 508. Specifically, the acoustic transducer 501 is a metal interdigital transducer.

[0077] The lead-out section 502 is used to realize the electrical connection between the electrode finger 508 and the pad, thereby realizing the electrical connection between the acoustic transducer 501 and the external circuit structure.

[0078] The electrode fingers 508 and the lead-out portions 502 are both made of one or more of molybdenum, aluminum, platinum, tungsten, gold, nickel, and silver. In some embodiments, the electrode fingers 508 and the lead-out portions 502 are both made of aluminum. Specifically, the electrode fingers 508 and the lead-out portions 502 are formed by depositing a metal film on a substrate 500 and patterning the metal film using photolithography and etching processes.

[0079] Continue to refer to Figure 4 A temperature compensation layer 503 is formed on the substrate 500, the temperature compensation layer 503 covers the acoustic transducer 501, and the temperature compensation layer 503 exposes at least a portion of the surface of the lead-out portion 502.

[0080] The temperature compensation layer 503 is used to offset the impact of temperature changes on filter performance, ensuring that the filter maintains stable performance under different temperature environments.

[0081] In some embodiments, the temperature compensation layer 503 exposes at least a portion of the surface of the lead-out portion 502, which helps to reduce the difficulty of making an electrical connection between the lead-out portion 502 and the pad. As an example, the temperature compensation layer 503 exposes a portion of the surface of the lead-out portion 502.

[0082] The temperature compensation layer 503 includes a silicon oxide layer or a composite material layer with silicon oxide as the main component. As an example, the temperature compensation layer 503 is a silicon oxide layer.

[0083] It should be noted that, on the one hand, the silicon oxide layer or the composite material layer with silicon oxide as the main component has a frequency temperature coefficient opposite to that of the substrate 500. Therefore, when the temperature compensation layer 503 is combined with the substrate 500, it can effectively counteract the influence of temperature changes on the filter frequency, making the frequency temperature coefficient of the filter tend to zero, thereby ensuring that the filter can maintain stable performance under different temperature environments. On the other hand, the elastic modulus of the silicon oxide layer or the composite material layer with silicon oxide as the main component changes with temperature in the opposite direction to the elastic modulus of the substrate 500. Therefore, the silicon oxide layer or the composite material layer with silicon oxide as the main component can compensate for the stress changes of the substrate 500 caused by thermal expansion.

[0084] Specifically, a composite material layer with silicon dioxide as the main component refers to a composite material layer in which the silicon dioxide content is higher than the content of any other single material in the composite material layer.

[0085] Specifically, the steps of forming the temperature compensation layer 503 include: forming a temperature compensation material layer (not shown) on the substrate 500, the temperature compensation material layer covering the acoustic transducer 501 and the lead-out portion 502; planarizing the temperature compensation material layer; after planarizing the temperature compensation material layer, patterning the temperature compensation material layer, forming an opening 515 in the temperature compensation material layer, the opening 515 exposing a portion of the surface of the lead-out portion 502, and the remaining temperature compensation material layer serving as the temperature compensation layer 503.

[0086] refer to Figures 5 to 7 A first passivation layer 504 with an interconnection window 509 is formed on the temperature compensation layer 503, and the interconnection window 509 exposes the lead-out portion 502 on the side of the temperature compensation layer 503.

[0087] The first passivation layer 504 serves not only to protect the temperature compensation layer 503, but also to adjust the operating frequency of the acoustic transducer 501. Specifically, the operating frequency of the acoustic transducer 501 can be adjusted by changing the thickness of the first passivation layer 504.

[0088] The first passivation layer 504 has an interconnect window 509, which exposes the lead-out portion 502 on the side of the temperature compensation layer 503.

[0089] Therefore, the first passivation layer 504 can also be used to define the area where the lead-out portion 502 connects to the pad.

[0090] The thickness of the first passivation layer 504 should not be too small. If the thickness of the first passivation layer 504 is too small, it may result in poor protection of the temperature compensation layer 503, thereby increasing the possibility of water vapor in the air entering the temperature compensation layer 503. Therefore, in some embodiments, the thickness of the first passivation layer 504 is greater than or equal to 80 angstroms. Specifically, the thickness of the first passivation layer 104 can be 80 angstroms or 500 angstroms.

[0091] In some embodiments, the first passivation layer 504 includes one or more layers selected from silicon nitride, aluminum oxide, silicon carbide, silicon carbide, aluminum nitride, gallium arsenide, and gallium nitride. As an example, the first passivation layer 504 is a silicon nitride layer.

[0092] Specifically, the silicon nitride layer, aluminum oxide layer, silicon carbide layer, silicon carbide layer, aluminum nitride layer, gallium arsenide layer, and gallium nitride layer all have dense crystal structures, which can form a continuous and pore-free thin film. Therefore, they can effectively protect the layer and reduce the possibility of water vapor in the air entering the temperature compensation layer 503.

[0093] refer to Figure 7In some embodiments, in the step of forming a first passivation layer 504 with interconnect windows 509 on the temperature compensation layer 503, the interconnect windows 509 include one or both of a first interconnect window 511 and a second interconnect window 512; the first interconnect window 511 also exposes a sidewall of the temperature compensation layer 503 adjacent to the lead-out portion 502, and a portion of the top surface connected to the exposed sidewall; the second interconnect window 512 is located on the side of the temperature compensation layer 503 and exposes a portion of the top surface of the lead-out portion 502.

[0094] It should be noted that the first interconnect window 511 also exposes the sidewall of the temperature compensation layer 503 adjacent to the lead-out portion 502 and the top surface connected to the exposed sidewall. Correspondingly, the subsequently formed pads cover the sidewall of the temperature compensation layer 503 adjacent to the lead-out portion 502 and the top surface connected to the exposed sidewall. Thus, the temperature compensation layer 503 isolates the pads from the adjacent electrode fingers 508, realizing the parallel connection of the acoustic transducers 501. The second interconnect window 512 is located on the side of the temperature compensation layer 503 and exposes part of the top surface of the lead-out portion 502. Correspondingly, the subsequently formed pads are located on part of the exposed top surface of the lead-out portion 502, which facilitates the pads to electrically connect the lead-out portion 502 to the adjacent electrode fingers 508, realizing the series connection of the acoustic transducers 501.

[0095] In some embodiments, at a local location on the substrate 500, a first interconnect window 511 exposes a sidewall of the temperature compensation layer 503 adjacent to the lead-out portion 502 and a portion of the top surface connected to the exposed sidewall. At other locations on the substrate 500, a second interconnect window 512 is located on the side of the temperature compensation layer 503 and exposes a portion of the top surface of the lead-out portion 502.

[0096] In other embodiments, at the location of the substrate, a first interconnect window exposes a sidewall of the temperature compensation layer adjacent to the lead-out portion and a portion of the top surface connected to the exposed sidewall; in other embodiments, at the location of the substrate, a second interconnect window is located on the side of the temperature compensation layer and exposes a portion of the top surface of the lead-out portion.

[0097] The steps for forming a first passivation layer 504 with interconnection windows 509 on the temperature compensation layer 503 are described in detail below with reference to the accompanying drawings.

[0098] refer to Figure 5 The first passivation layer 504 is formed covering the temperature compensation layer 503 and the lead-out portion 502.

[0099] In some embodiments, the process of forming the first passivation layer 504 on the temperature compensation layer 503 includes physical vapor deposition, chemical vapor deposition, or atomic layer deposition.

[0100] It should be noted that physical vapor deposition, chemical vapor deposition, and atomic layer deposition all have the characteristic of high film deposition density. Therefore, the first passivation layer 504 formed by physical vapor deposition has a high density.

[0101] refer to Figure 6 Before patterning the first passivation layer 504, a mask layer 517 with a mask opening 516 is formed on the first passivation layer 504, the mask opening 516 exposing the first passivation layer 504 covering the lead-out portion 502 on the side of the temperature compensation layer 503.

[0102] The mask opening 516 is used to define the position and shape of the subsequent pads, and also facilitates the subsequent removal of the first passivation layer 504 at the bottom of the mask opening 516.

[0103] The mask opening 516 exposes the first passivation layer 504 covering the lead-out portion 502 on the side of the temperature compensation layer 503, so that the first passivation layer 504 covering the lead-out portion 502 on the side of the temperature compensation layer 503 can be removed, so that the lead-out portion 502 on the side of the temperature compensation layer 503 can be exposed, thereby enabling the pads to electrically connect to the lead-out portion 502.

[0104] The mask layer 517 is used as a mask for forming the patterned first passivation layer 504 and pads.

[0105] In some embodiments, the mask layer 517 is made of photoresist. Photoresist has high resolution, allowing precise control of the opening size of the mask aperture 516; simultaneously, photoresist is easy to remove, reducing process complexity and thus improving production efficiency. In other embodiments, the mask layer may also be made of other materials suitable for use as etching masks and easily removable.

[0106] In some embodiments, in the step of forming a mask layer 517 with a mask opening 516 on the first passivation layer 504, the included angle D between the sidewall of the mask opening 516 and the top surface of the lead-out portion 502 (e.g., ...) Figure 6 (As shown) forms an acute angle.

[0107] The sidewall of the mask opening 516 refers to the sidewall of the mask layer 517.

[0108] It should be noted that the angle D between the sidewall of the mask opening 516 and the top surface of the lead-out portion 502 is an acute angle, that is, the inclination of the sidewall of the mask layer 517 is large. During the formation of the pad material layer, the pad material layer is not easily formed on the sidewall of the mask layer 517. Therefore, when the pad material layer on the top of the mask layer 517 is removed by the stripping process, the stripping process is easier to carry out.

[0109] refer to Figure 7 The first passivation layer 504 is graphically visualized, and an interconnection window 509 is formed in the first passivation layer 504.

[0110] Interconnect window 509 provides space for electrical connections between pads and leads 502.

[0111] Specifically, in the step of patterning the first passivation layer 504, the first passivation layer 504 at the bottom of the mask opening 516 is removed, and an interconnection window 509 communicating with the mask opening 516 is formed in the first passivation layer 504.

[0112] It should be noted that the mask layer 517 serves as the mask for forming the patterned first passivation layer 504 and the pads, meaning that the patterned first passivation layer 504 and the pads share a single photomask, which helps save costs. In addition, the shared mask layer 517 between the patterned first passivation layer 504 and the pads reduces the number of times the mask layer is formed, thereby reducing the probability of residues from the mask layer 517 on the surface of the first passivation layer 504, and thus improving the formation quality of the second passivation layer.

[0113] In some embodiments, the process of removing the first passivation layer 504 at the bottom of the mask opening 516 includes a dry etching process. Dry etching has anisotropic etching characteristics, making the etching more directional, which is beneficial for improving the morphology and dimensional accuracy of the interconnect window 509.

[0114] In other embodiments, after forming a first passivation layer with interconnect windows on the temperature compensation layer, a mask layer with mask openings can be formed on the first passivation layer, that is, different mask layers can be used to form interconnect windows and pads.

[0115] refer to Figures 8 to 10 A pad 505 is formed in the interconnect window 509, and the pad 505 is electrically connected to the lead-out portion 502.

[0116] Pad 505 is used for electrical connection lead-out section 502 to connect electrical connection lead-out section 502 to external circuit.

[0117] It should be noted that the first passivation layer 504 is formed on the temperature compensation layer 503 first, and then the pad 505 is formed. This avoids the influence of the formation process of the pad 505 on the formation quality of the first passivation layer 504 on the temperature compensation layer 503, resulting in a higher formation quality of the first passivation layer 504. Consequently, the protective effect of the first passivation layer 504 on the temperature compensation layer 503 is guaranteed, and the possibility of water vapor in the air entering the temperature compensation layer 503 is reduced. This improves the problems of high acceleration temperature and humidity and bias voltage test failure of the filter, thereby improving the performance of the filter.

[0118] It should be noted that, since the interconnect window 509 in the first passivation layer 504 includes one or both of the first interconnect window 511 and the second interconnect window 512, accordingly, refer to Figure 9 Pad 505 includes one or both of a first pad 513 and a second pad 514: the first pad 513 is located in the first interconnect window 511 (e.g., Figure 7 As shown), the first pad 513 covers the sidewall of the temperature compensation layer 503 adjacent to the lead-out portion 502, and the top surface connected to the exposed sidewall; the second pad 514 is located in the second interconnect window 512 (as shown). Figure 7 As shown in the figure, the second pad 514 is located on the side of the temperature compensation layer 503 and covers part of the top surface of the lead-out portion 502.

[0119] Specifically, the first pad 513 covers the sidewall of the temperature compensation layer 503 adjacent to the lead-out portion 502 and the top surface connected to the exposed sidewall. Therefore, the temperature compensation layer 503 isolates the pad 505 from the adjacent electrode finger 508, realizing the parallel connection of the acoustic transducer 501.

[0120] The second pad 514 is used to electrically connect the lead-out part 502 with the adjacent electrode finger 508, thereby realizing the series connection of the acoustic transducer 501.

[0121] In some embodiments, the material of pad 505 includes one or more of aluminum, copper, gold, titanium, nickel, silver, and tungsten. It should be noted that aluminum, copper, gold, titanium, nickel, silver, and tungsten all have good electrical conductivity. As an example, the material of pad 505 is aluminum.

[0122] As an example, the pads include both a first pad 513 and a second pad 514.

[0123] In other embodiments, the pad may include only the first pad, or the pad may include only the second pad.

[0124] Specifically, the step of forming the pad 505 in the interconnect window 509 includes: referencing Figure 8A mask opening 516 is formed on the first passivation layer 504 (e.g., Figure 7 The mask layer 517 (shown) is configured such that the mask opening 516 communicates with the interconnect window 509 formed in the first passivation layer 504, and the mask opening 516 exposes the lead-out portion 502 on the side of the temperature compensation layer 503 via the interconnect window 509; Continuing to refer to... Figure 8 A pad material layer 518 is formed in the interconnect window 509, and the pad material layer 518 is also located on the mask layer 517; Reference Figures 9 to 10 The mask layer 517 and the pad material layer 518 located on the mask layer 517 are removed by a stripping process, and the remaining pad material layer 518 located in the interconnect window 509 serves as the pad 505.

[0125] The mask opening 516 is used to define the position and shape of the pad 505, and also facilitates the subsequent removal of the first passivation layer 504 at the bottom of the mask opening 516.

[0126] The mask layer 517 is used as a mask to form the patterned first passivation layer 504 and pad 505.

[0127] The mask opening 516 is connected to the interconnect window 509 formed in the first passivation layer 504. No additional alignment steps between the interconnect window 509 and the mask opening 516 are required. When forming the pad 505, the pad material layer 518 can be deposited directly in the mask opening 516 and the interconnect window 509, thereby simplifying the process and reducing defects caused by alignment errors.

[0128] The pad material layer 518 is used to form the pad 505.

[0129] The lift-off process omits the etching step, which on the one hand helps reduce production time and improve production efficiency; on the other hand, it easily avoids pattern distortion problems that occur during the etching process, thereby improving the quality of the formed pad 505.

[0130] refer to Figures 9 to 10 In the step of forming pads 505 in the interconnect window 504, a gap 510 (e.g., ...) is provided between the first passivation layer 504 and the pads 505. Figure 10 (As shown).

[0131] It should be noted that during the formation of the pad 105, a mask layer 517 with a mask opening 516 is formed on the top of the first passivation layer 104. The angle between the sidewall of the mask opening and the top surface of the lead-out portion 102 is an acute angle, that is, the inclination of the sidewall of the mask layer 517 is large. Therefore, the material of the pad 505 is not easily formed on the mask layer 517, resulting in a gap between the pad 505 and the mask layer 517. At the same time, the mask layer 517 covers the first passivation layer 504, and there is a gap 510 between the first passivation layer 504 and the pad 505.

[0132] Continue to refer to Figures 9 to 10 After forming the pad 505, the forming method further includes removing the mask layer 517.

[0133] Specifically, the mask layer 517 is removed to provide space for the subsequent formation of a second passivation layer on the first passivation layer 504 and the pad 505.

[0134] refer to Figures 11 to 12 A second passivation layer 506 is formed covering the first passivation layer 504 and the pad 505, the second passivation layer 506 exposing at least a portion of the surface of the pad 505.

[0135] The second passivation layer 506 protects the first passivation layer 504 and the pads 505, helping to prevent them from being exposed to air. This reduces the probability of water vapor and pollutants in the air adhering to the first passivation layer 504 and the pads 505. It also helps to adjust the operating frequency of the acoustic transducer 501. Specifically, the operating frequency of the acoustic transducer 501 can be adjusted by changing the thickness of the second passivation layer 506.

[0136] In some embodiments, during the step of forming pads 505 in the interconnect window 504, a gap 510 is provided between the first passivation layer 504 and the pads 505.

[0137] Therefore, in some embodiments, in the step of forming a second passivation layer 506 covering the first passivation layer 504 and the pad 505, the second passivation layer 506 also fills the gap 510, thereby reducing the possibility of water vapor in the air entering the temperature compensation layer 503 from the gap 510.

[0138] In some embodiments, the density of the first passivation layer 504 is greater than that of the second passivation layer 506. Because the density of the first passivation layer 504 is greater, the first passivation layer 504 can protect the temperature compensation layer 503, thereby reducing the possibility of water vapor in the air entering the temperature compensation layer 503 through the first passivation layer 504.

[0139] In some embodiments, the second passivation layer 506 includes one or more layers selected from silicon nitride, silicon oxide, aluminum oxide, silicon carbide, silicon carbide, aluminum nitride, gallium arsenide, and gallium nitride. As an example, the second passivation layer 506 is a silicon nitride layer.

[0140] The silicon nitride layer, silicon oxide layer, aluminum oxide layer, silicon carbide layer, silicon carbide layer, aluminum nitride layer, gallium arsenide layer, and gallium nitride layer all have a dense crystal structure and can form a continuous and pore-free thin film. Therefore, they can effectively protect the layer and reduce the possibility of water vapor in the air entering the temperature compensation layer 503.

[0141] The thickness of the second passivation layer 506 should not be too small. If the thickness of the second passivation layer 506 is too small, the thickness of the second passivation layer 506 filling the gap 510 will also be too small, thereby increasing the possibility that water vapor in the air will enter the temperature compensation layer 503 through the gap 510, which in turn increases the risk of filter failure during high-acceleration temperature and humidity and bias voltage tests. Therefore, in some embodiments, the thickness of the second passivation layer 506 is greater than or equal to 150 angstroms. Specifically, the thickness of the second passivation layer 106 can be 150 angstroms, 300 angstroms, or 1000 angstroms.

[0142] In some embodiments, the second passivation layer 506 exposes at least a portion of the surface of the pad 505, facilitating connection between the pad 505 and external circuitry.

[0143] As an example, the second passivation layer 506 exposes a portion of the surface of the pad 505.

[0144] The filter structure of this embodiment can be formed using the filter structure formation method of the aforementioned embodiment, or it can be formed using other filter structure formation methods, which will not be described again in this embodiment.

[0145] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A filter, characterized in that, include: Base; An acoustic transducer is located on the substrate, and the acoustic transducer includes an outlet portion; A temperature compensation layer covers the acoustic transducer and the substrate, and the temperature compensation layer exposes at least a portion of the surface of the lead-out portion; A first passivation layer covers the temperature compensation layer and exposes the lead-out portion on the side of the temperature compensation layer, and the surface of the lead-out portion exposed by the first passivation layer serves as the interconnection area of ​​the lead-out portion; A pad is located on the side of the first passivation layer and covers the interconnect area of ​​the lead-out portion; the pad is electrically connected to the lead-out portion. A second passivation layer covers the first passivation layer and the pads, with the second passivation layer exposing at least a portion of the surface of the pads.

2. The filter as described in claim 1, characterized in that, There is a gap between the first passivation layer and the pad; The second passivation layer also fills the gap.

3. The filter as described in claim 1, characterized in that, The density of the first passivation layer is greater than that of the second passivation layer.

4. The filter as described in claim 1, characterized in that, The acoustic transducer includes interdigitated electrodes, each interdigitated electrode including a lead-out portion and an electrode finger located on the side of the lead-out portion, and the lead-out portion is electrically connected to the electrode finger.

5. The filter as described in claim 1, characterized in that, The first passivation layer includes one or two of the following: The first passivation layer covers the top surface and sidewalls of the temperature compensation layer; The first passivation layer covers a portion of the top surface of the temperature compensation layer and exposes the sidewalls of the temperature compensation layer adjacent to the interconnection region, as well as a portion of the top surface connected to the exposed sidewalls.

6. The filter as described in any one of claims 1 to 5, characterized in that, The first passivation layer includes one or more of the following: silicon nitride layer, aluminum oxide layer, silicon carbide layer, silicon oxycarbonate layer, aluminum nitride layer, gallium arsenide layer, and gallium nitride layer.

7. The filter as described in any one of claims 1 to 5, characterized in that, The second passivation layer includes one or more of the following: silicon nitride layer, silicon oxide layer, aluminum oxide layer, silicon carbide layer, silicon carbide layer, aluminum nitride layer, gallium arsenide layer, and gallium nitride layer.

8. The filter as described in any one of claims 1 to 5, characterized in that, The thickness of the first passivation layer is greater than or equal to 80 angstroms.

9. The filter as described in any one of claims 1 to 5, characterized in that, The thickness of the second passivation layer is greater than or equal to 150 angstroms.

10. An electronic device, characterized in that, Includes the filter as described in any one of claims 1 to 9.

11. A method for forming a filter, characterized in that, include: A substrate is provided on which an acoustic transducer is formed, the acoustic transducer including an outlet portion; A temperature compensation layer is formed on the substrate, the temperature compensation layer covers the acoustic transducer, and the temperature compensation layer exposes at least a portion of the surface of the lead-out portion; A first passivation layer with interconnect windows is formed on the temperature compensation layer, the interconnect windows exposing the lead-out portion on the side of the temperature compensation layer; Pads are formed in the interconnect window, and the pads are electrically connected to the leads. A second passivation layer is formed covering the first passivation layer and the pads, the second passivation layer exposing at least a portion of the surface of the pads.

12. The method for forming a filter as described in claim 11, characterized in that, The step of forming the pad in the interconnect window includes: forming a mask layer with a mask opening on the first passivation layer; wherein the mask opening is connected to the interconnect window formed in the first passivation layer, and the mask opening exposes the lead-out portion on the side of the temperature compensation layer through the interconnect window; A pad material layer is formed in the interconnect window, and the pad material layer is also located on the mask layer; The mask layer and the pad material layer on the mask layer are removed by a stripping process, and the remaining pad material layer in the interconnect window is used as a pad. After forming the pads, the forming method further includes removing the mask layer.

13. The method for forming a filter as described in claim 12, characterized in that, The step of forming a first passivation layer with interconnect windows on the temperature compensation layer includes: forming a first passivation layer covering the temperature compensation layer and the lead-out portion; patterning the first passivation layer and forming interconnect windows in the first passivation layer; Before patterning the first passivation layer, a mask layer with a mask opening is formed on the first passivation layer, the mask opening exposing the first passivation layer covering the lead-out portion covering the side of the temperature compensation layer; In the step of graphically representing the first passivation layer, the first passivation layer at the bottom of the mask opening is removed, and an interconnection window communicating with the mask opening is formed in the first passivation layer.

14. The method for forming a filter according to any one of claims 11 to 13, characterized in that, The process for forming the first passivation layer on the temperature compensation layer includes physical vapor deposition, chemical vapor deposition, or atomic layer deposition.

15. The method for forming a filter as described in claim 12 or 13, characterized in that, The material of the mask layer includes photoresist.

16. The method for forming a filter as described in claim 13, characterized in that, The process for removing the first passivation layer at the bottom of the mask opening includes a dry etching process.

17. The method for forming a filter as described in claim 12, characterized in that, In the step of forming a mask layer with a mask opening on the first passivation layer, the angle between the sidewall of the mask opening and the top surface of the lead-out portion is an acute angle.

18. The method for forming a filter according to any one of claims 11 to 13, characterized in that, In the step of forming a first passivation layer with interconnect windows on the temperature compensation layer, the interconnect windows include one or both of a first interconnect window and a second interconnect window; The first interconnect window also exposes the sidewall of the temperature compensation layer adjacent to the lead-out portion, and the top surface portion connected to the exposed sidewall; The second interconnect window is located on the side of the temperature compensation layer and exposes part of the top surface of the lead-out portion.

19. The method for forming a filter as described in claim 11, characterized in that, In the step of forming pads in the interconnect window, there is a gap between the first passivation layer and the pads; In the step of forming a second passivation layer covering the first passivation layer and the pads, the second passivation layer also fills the gap.

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