Preparation method of surface acoustic wave filter chip with frequency adjustment structure

Abstract

The invention relates to a preparation method of a surface acoustic wave filter chip with a frequency adjustment structure, and the method comprises the following steps: S1, carrying out the spin coating of a layer of photoresist on one side surface of a substrate, and carrying out the photoetching operation for patterning; s2, evaporating a layer of titanium-aluminum electrode on one side surface of the patterned substrate, removing the photoresist, completing electrode patterning, and forming an interdigital metal region on one side surface of the substrate; and S3, sputtering silicon dioxide on one side surface of the substrate in a magnetron sputtering manner, so that the substrate between the interdigital metal regions is filled with the silicon dioxide filling layer, and a silicon dioxide protection layer is formed on the interdigital metal regions and the silicon dioxide filling layer. According to the surface acoustic wave filter, the combination mode of the interdigital metal area and the silicon dioxide material is ingeniously designed, complex trim operation is avoided, the frequency characteristic of the surface acoustic wave filter is effectively improved, meanwhile, the structural stability and the production efficiency of the device are guaranteed, and the production cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of microelectronics and surface acoustic wave (SAW), and in particular to a method for preparing a surface acoustic wave filter chip with a frequency adjustment structure. Background Art

[0002] Frequency adjustment is a key step in the existing surface acoustic wave filter manufacturing process. Traditional methods usually include using SiO 2 Perform passivation to reduce the frequency, or rely on precision trim equipment to thin the metal electrode to increase the frequency. However, the trim operation is not only technically complex and requires high skills from the operator, but also highly dependent on the equipment, increasing production costs and process difficulty. In addition, the trim process rate is slow, and long-term operation can easily lead to excessive local temperatures, which may cause thermal stress accumulation in the piezoelectric substrate, and ultimately lead to substrate fragmentation, seriously affecting product reliability and production yield. Summary of the invention

[0003] In order to solve one or more technical problems existing in the prior art, the present invention provides a method for preparing a surface acoustic wave filter chip with a frequency adjustment structure.

[0004] The technical solution of the present invention to solve the above technical problem is as follows: A method for preparing a surface acoustic wave filter chip with a frequency adjustment structure comprises the following steps:

[0005] S1, spin coating a layer of photoresist on one side of the substrate, and then performing photolithography operation for patterning;

[0006] S2, vapor-depositing a layer of titanium aluminum electrode on one side of the substrate that has been patterned, and then removing the photoresist to complete the electrode patterning, forming an interdigitated metal region on one side of the substrate;

[0007] S3, sputtering silicon dioxide on one side of the substrate by magnetron sputtering, so that the substrate between the interdigitated metal regions is filled with a silicon dioxide filling layer, and a silicon dioxide protective layer is formed on the interdigitated metal regions and the silicon dioxide filling layer.

[0008] The beneficial effects of the present invention are as follows: the preparation method of the present invention, by cleverly designing the combination mode of the interdigitated metal region and the silicon dioxide material, not only avoids the complicated trim operation, but also effectively improves the frequency characteristics of the surface acoustic wave filter, while ensuring the structural stability and production efficiency of the device, reducing the production cost, and providing a new technical path for the research and development of high-performance filters.

[0009] Based on the above technical solution, the present invention can also be improved as follows.

[0010] Furthermore, S2 also includes spin coating a layer of photoresist on one side of the substrate where the interdigitated metal region is formed, and then performing a photolithography operation so that the pressure welding electrode region in the interdigitated metal region is exposed and the interdigitated transducer region in the interdigitated metal region is protected by the photoresist; and again using an electron beam evaporation device to evaporate a layer of titanium aluminum electrode so that the pressure welding electrode region has two layers of titanium aluminum electrodes, and then removing the photoresist.

[0011] Furthermore, in the pressure welding electrode region, the thickness of the titanium aluminum electrode located at the lower layer is the same as the thickness of the titanium aluminum electrode in the interdigital transducer region.

[0012] Furthermore, in the pressure welding electrode region, the thickness of the titanium-aluminum electrode located in the upper layer is smaller than the thickness of the titanium-aluminum electrode located in the lower layer.

[0013] Furthermore, the titanium-aluminum electrode includes a titanium film and an aluminum film, and the titanium film is located below the aluminum film.

[0014] Furthermore, the method further includes S4, thinning the silicon dioxide protective layer by using a chemical mechanical polishing process to meet the frequency requirement of the surface acoustic wave filter chip.

[0015] The beneficial effect of adopting the above further scheme is that the silicon dioxide in the gaps of the metal fingers changes the propagation mode of the sound waves and increases the frequency; the silicon dioxide on the surface of the metal fingers increases the mass load and reduces the frequency. The final frequency is determined by the competitive relationship between the two, and the frequency can be accurately increased by adjusting the thickness of the polished silicon dioxide.

[0016] Furthermore, the silicon dioxide protective layer is thinned and covers the interdigital transducer area of ​​the interdigital metal area and the silicon dioxide filling layer, and the surface of the thinned silicon dioxide protective layer is flush with or lower than the surface of the pressure welding electrode area in the interdigital metal area.

[0017] Furthermore, the thickness of the silicon dioxide protective layer after thinning is 0.

[0018] Further, in S2, the photoresist is removed by a lift-off process.

[0019] Further, in S2, an electron beam evaporation device is used to evaporate a layer of titanium aluminum electrode on one side of the patterned substrate.

[0020] The preparation method of the present invention has the following advantages:

[0021] (1) Simplify the process flow: avoid complex trim operations, reduce equipment dependence, and reduce production costs and cycles.

[0022] (2) Improve frequency adjustment accuracy: Through material filling and surface treatment, fine frequency control is achieved, improving product performance consistency.

[0023] (3) Enhanced structural stability: The filling of silicon dioxide enhances the structural strength of the chip and reduces the risk of damage caused by external factors.

[0024] (4) Improve production efficiency and yield: Reduce the scrap rate caused by improper trim operation and improve overall production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The structure of step 1 of the present invention is shown in FIG. Figure 1 ;

[0026] Figure 2 The structure of step 1 of the present invention is shown in FIG. Figure 2 ;

[0027] Figure 3 The structure of step 2 of the present invention is shown in FIG. Figure 1 ;

[0028] Figure 4 The structure of step 2 of the present invention is shown in FIG. Figure 2 ;

[0029] Figure 5 The structure of step 2 of the present invention is shown in FIG. Figure 3 ;

[0030] Figure 6 The structure of step 2 of the present invention is shown in FIG. Figure 4 ;

[0031] Figure 7 for Figure 6 A schematic diagram of the partially enlarged structure;

[0032] Figure 8 The structure of step 2 of the present invention is shown in FIG. Figure 5 ;

[0033] Fig. 9 for Figure 8 A schematic diagram of the partially enlarged structure;

[0034] Fig.10 This is a schematic diagram of the structure of step 3 of the present invention;

[0035] Fig.11 for Fig.10 A schematic diagram of the partially enlarged structure;

[0036] Fig.12 The structure of step 4 of the present invention is shown in FIG. Figure 1 ;

[0037] Fig.13 for Fig.12 A schematic diagram of the partially enlarged structure;

[0038] Fig.14 The structure of step 4 of the present invention is shown in FIG. Figure 2 ;

[0039] Fig.15 for Fig.14 Schematic diagram of the partially enlarged structure.

[0040] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0041] 1. Substrate; 2. First photoresist; 3. Second photoresist; 4. Titanium film; 5. Aluminum film; 6. Silicon dioxide. DETAILED DESCRIPTION

[0042] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0043] like Figure 1 to Figure 15 As shown, a method for preparing a surface acoustic wave filter chip with a frequency adjustment structure in this embodiment includes the following steps:

[0044] S1, spin-coating a layer of photoresist (the photoresist is the first photoresist 2) on one side of the substrate 1, and then performing a photolithography operation for patterning;

[0045] S2, vapor-depositing a layer of titanium aluminum electrode on one side of the patterned substrate 1, then removing the photoresist to complete the electrode patterning, and forming an interdigitated metal region on one side of the substrate;

[0046] S3, using magnetron sputtering to sputter silicon dioxide 6 on one side of the substrate 1, so that the substrate between the interdigitated metal regions is filled with a silicon dioxide filling layer, so that a silicon dioxide protective layer is formed on the interdigitated metal regions and the silicon dioxide filling layer. The thickness of the silicon dioxide filling layer should not be less than the height of the interdigitated metal regions, so that the gaps in the interdigitated metal regions are filled with silicon dioxide.

[0047] like Figures 5 to 9 As shown, S2 of this embodiment also includes spin coating a layer of photoresist (this photoresist is the second photoresist 3) on one side of the substrate 1 where the interdigitated metal region is formed, and then performing a photolithography operation so that the pressure welding electrode region in the interdigitated metal region is exposed and the interdigitated transducer region in the interdigitated metal region is protected by the photoresist; and again using an electron beam evaporation device to evaporate a layer of titanium aluminum electrode so that the pressure welding electrode region has two layers of titanium aluminum electrodes, and then removing the photoresist.

[0048] Specifically, in S2, the photoresist is removed by a lift-off process. In S2, an electron beam evaporation device is used to evaporate a layer of titanium aluminum electrode on one side of the substrate 1 that has been subjected to patterning.

[0049] like Figure 8 and Fig. 9 As shown, in the pressure welding electrode region of this embodiment, the thickness of the titanium aluminum electrode located in the lower layer is the same as the thickness of the titanium aluminum electrode in the interdigital transducer region.

[0050] like Figure 8 and Fig. 9 As shown, in the pressure welding electrode region of this embodiment, the thickness of the titanium-aluminum electrode located in the upper layer is less than the thickness of the titanium-aluminum electrode located in the lower layer.

[0051] like Figure 3 to Figure 9 As shown, the titanium-aluminum electrode of this embodiment includes a titanium film 4 and an aluminum film 5 , and the titanium film 4 is located below the aluminum film 5 .

[0052] like Figure 12 to Figure 15 As shown, the preparation method of this embodiment also includes S4, using a chemical mechanical polishing process to thin the silicon dioxide protective layer to meet the frequency requirements of the surface acoustic filter chip. Specifically, a CMP device is used to thin the silicon dioxide on the surface. The silicon dioxide 6 in the gaps of the metal fingers changes the propagation mode of the sound waves and increases the frequency; the silicon dioxide 6 on the surface of the metal fingers increases the mass load and reduces the frequency. The final frequency is determined by the competitive relationship between the two, and the frequency can be accurately increased by adjusting the thickness of the polished silicon dioxide 6.

[0053] like Fig.12 and Fig.13 As shown, the silicon dioxide protective layer of this embodiment is covered on the interdigital transducer area and the silicon dioxide filling layer in the interdigital metal area after thinning, and the surface of the thinned silicon dioxide protective layer is flush with or lower than the surface of the pressure welding electrode area in the interdigital metal area.

[0054] like Fig.14 and Fig.15 As shown, the thickness of the silicon dioxide protective layer in this embodiment is 0 after thinning.

[0055] The preparation method of this embodiment avoids complicated trim operations and effectively improves the frequency characteristics of the surface acoustic wave filter by cleverly designing the combination method of the interdigitated metal area and the silicon dioxide material. At the same time, it ensures the structural stability and production efficiency of the device, reduces the production cost and cycle, and provides a new technical path for the research and development of high-performance filters.

[0056] In the description of the present invention, it is necessary to understand that the orientation or positional relationship indicated by the terms "thickness", "height", "top", "bottom", "inside", "outside", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0057] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0058] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0059] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0060] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0061] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a surface acoustic wave filter chip having a frequency adjustment structure, characterized in that: The following steps are involved: S1, spin coating a layer of photoresist on one side of the substrate, and then performing photolithography operation for patterning; S2, vapor-depositing a layer of titanium aluminum electrode on one side of the substrate that has been patterned, and then removing the photoresist to complete the electrode patterning, forming an interdigitated metal region on one side of the substrate; S3, sputtering silicon dioxide on one side of the substrate by magnetron sputtering, so that the substrate between the interdigitated metal regions is filled with a silicon dioxide filling layer, and a silicon dioxide protective layer is formed on the interdigitated metal regions and the silicon dioxide filling layer.

2. The method for preparing a surface acoustic wave filter chip having a frequency adjustment structure according to claim 1, characterized in that: S2 also includes spin coating a layer of photoresist on one side of the substrate where the interdigitated metal region is formed, and then performing a photolithography operation so that the bonding electrode region in the interdigitated metal region is exposed and the interdigitated transducer region in the interdigitated metal region is protected by the photoresist; and again using an electron beam evaporation device to evaporate a layer of titanium aluminum electrode so that the bonding electrode region has two layers of titanium aluminum electrodes, and then removing the photoresist.

3. The method for preparing a surface acoustic wave filter chip having a frequency adjustment structure according to claim 2, characterized in that: In the pressure welding electrode region, the thickness of the titanium aluminum electrode located at the lower layer is the same as the thickness of the titanium aluminum electrode in the interdigital transducer region.

4. The method for preparing a surface acoustic wave filter chip having a frequency adjustment structure according to claim 2, characterized in that: In the pressure welding electrode region, the thickness of the titanium-aluminum electrode located at the upper layer is smaller than the thickness of the titanium-aluminum electrode located at the lower layer.

5. The method for preparing a surface acoustic wave filter chip having a frequency adjustment structure according to claim 1, characterized in that: The titanium-aluminum electrode comprises a titanium film and an aluminum film, and the titanium film is located below the aluminum film.

6. The method for preparing a surface acoustic wave filter chip having a frequency adjustment structure according to claim 1, characterized in that: It also includes S4, which uses a chemical mechanical polishing process to thin the silicon dioxide protective layer to meet the frequency requirements of the surface acoustic wave filter chip.

7. The method for preparing a surface acoustic wave filter chip having a frequency adjustment structure according to claim 6, characterized in that: The silicon dioxide protective layer is thinned and covers the interdigital transducer region of the interdigital metal region and the silicon dioxide filling layer. The surface of the thinned silicon dioxide protective layer is flush with or lower than the surface of the pressure welding electrode region in the interdigital metal region.

8. The method for preparing a surface acoustic wave filter chip with a frequency adjustment structure according to claim 6, characterized in that: The thickness of the silicon dioxide protective layer after thinning is 0.

9. The method for preparing a surface acoustic wave filter chip with a frequency adjustment structure according to claim 1, characterized in that: In S2, the photoresist is removed using a lift-off process.

10. The method for preparing a surface acoustic wave filter chip with a frequency adjustment structure according to claim 1, characterized in that: In S2, an electron beam evaporation device is used to evaporate a layer of titanium aluminum electrode on one side of the patterned substrate.

Images