Manufacturing method for laterally excited bulk acoustic wave filter, and radio-frequency module

Abstract

The present invention is applicable to the technical field of semiconductor processes, and particularly relates to a manufacturing method for a laterally excited bulk acoustic wave filter, and a radio-frequency module. The manufacturing method uses the respective excellent characteristics of silicon-based glass and photosensitive glass so as to obtain crystallized glass as a sacrificial layer by means of exposing and annealing the photosensitive glass during manufacturing, thereby implementing pattern transfer. This process does not involve cavity lithography, etching or coating, thus reduces process steps, thereby reducing difficulty and costs, and improving the yield and structural stability of a filter; in addition, crystallized glass and uncrystallized photosensitive glass have high etching selectivity and extremely low parasitic resistance and capacitance, so that cavity etching can be simply and accurately controlled so as to obtain an ideal cavity structure, and device insertion loss can be reduced to improve the overall performance of the filter.

Description

Manufacturing method of transversely excited bulk acoustic wave filter and radio frequency module TECHNICAL FIELD

[0001] The present application belongs to the technical field of semiconductor process, and particularly relates to a manufacturing method of transversely excited bulk acoustic wave filter and a radio frequency module. BACKGROUND

[0002] With the popularization of 5G mobile communication technology, 6G is rapidly advancing towards commercialization. One of the features of 6G technology is high data transmission rate, large network capacity and ultra-low delay, which requires the filter as a radio frequency front-end module to have high frequency, large bandwidth and low loss. In the existing technical solution, the transversely excited bulk acoustic wave filter (XBAR) is considered as the best technical solution because of its high quality factor, high frequency, small size and low insertion loss.

[0003] The typical structure of the transversely excited bulk acoustic wave filter from bottom to top is substrate material, cavity, piezoelectric material and interdigital transducer, wherein the cavity is a key structure for the operation of the transversely excited thin film bulk acoustic resonator, which plays a role in mode coupling, frequency selection and energy reflection.

[0004] At present, there are two typical technical solutions for the cavity of the transversely excited bulk acoustic wave filter. One is to first form a cavity on the surface of the substrate material, then fill a sacrificial layer into the cavity, then complete the preparation of the interdigital transducer electrode and the piezoelectric material on the upper surface, and finally release the sacrificial layer to obtain the cavity. The other is to directly form a sacrificial layer on the surface of the substrate material, then complete the preparation of the interdigital transducer electrode and the piezoelectric material on the upper surface, and finally release part of the sacrificial layer to obtain the cavity.

[0005] However, the first solution needs to perform process steps such as exposure, lithography, etching and plating on the surface of the substrate to pre-embed the cavity, and use the CMP process to grind the surface of the plated film to make the surface flat. This solution has many process steps, high difficulty, high manufacturing cost and low overall device yield. Although the second solution does not need to pre-embed the cavity, the cavity etching process needs to be precisely controlled, which is difficult and has a low device yield. SUMMARY

[0006] The present application provides a manufacturing method of transversely excited bulk acoustic wave filter and a radio frequency module, which aims to solve the technical problems of high difficulty and low yield in the existing manufacturing method of transversely excited bulk acoustic wave filter.

[0007] To solve the above technical problems, in a first aspect, the present application provides a manufacturing method of transversely excited bulk acoustic wave filter, which comprises the following steps:

[0008] S1, providing a silicon-based substrate material and a photosensitive glass;

[0009] S2, bonding the lower surface of the photosensitive glass with the upper surface of the silicon-based substrate material by a bonding process;

[0010] S3, mechanically thinning and polishing the upper surface of the photosensitive glass;

[0011] S4, exposing and annealing the photosensitive glass to crystallize a portion of the photosensitive glass into a crystallized glass;

[0012] S5, preparing a piezoelectric material on the upper surface of the photosensitive glass;

[0013] S6, growing a metal on the upper surface of the piezoelectric material and forming an interdigital transducer by a patterning process;

[0014] S7, etching the piezoelectric material to form an etching via hole penetrating through the piezoelectric material and connecting the crystallized glass with the outside;

[0015] S8, releasing the sacrificial layer of the crystallized glass through the etching via hole to obtain a series-parallel resonator with a cavity;

[0016] S9, connecting a plurality of the series-parallel resonators according to a preset electrical rule to obtain a lateral excitation bulk acoustic wave filter.

[0017] Further, the bonding material used in the bonding process in step S2 is at least one of silicon oxide and aluminum oxide.

[0018] Further, in step S4, the thickness of the crystallized glass is controlled to be 0.1-10 um by controlling the time of exposure and annealing of the photosensitive glass.

[0019] Further, the method for preparing the piezoelectric material on the upper surface of the photosensitive glass in step S5 is magnetron sputtering or a bonding process.

[0020] Further, in step S6, the method for growing the metal includes at least one of magnetron sputtering and chemical vapor deposition, and the patterning process includes at least one of photolithography stripping and photolithography etching.

[0021] Further, in step S7, the method for etching the piezoelectric material includes at least one of gas etching and liquid etching.

[0022] Further, the piezoelectric material is lithium tantalate single crystal or lithium niobate single crystal, and the thickness of the piezoelectric material is 0.1-1 um.

[0023] Further, the metal constituting the interdigital transducer is at least one of gold, aluminum, copper, silver, and titanium, and the thickness of the interdigital transducer is 0.1 um to 20 times the thickness of the piezoelectric material.

[0024] In a second aspect, the present application also provides a radio frequency module comprising the transversely excited bulk acoustic wave filter manufactured by the method as described in any one of the above.

[0025] The present application has the advantages that a transversely excited bulk acoustic wave filter manufacturing method is provided, which utilizes the excellent characteristics of silicon and photosensitive glass, exposes and anneals the photosensitive glass to obtain crystallized glass as a sacrifice layer, and completes patterned transfer, which does not involve cavity photolithography, etching, and plating, reduces the process steps, can reduce the difficulty and cost, and improves the yield and structural stability of the filter; meanwhile, the crystallized glass has high etching selectivity and extremely low parasitic resistance and capacitance compared with the non-crystallized photosensitive glass, can simply and accurately control cavity etching, obtain an ideal cavity structure, and reduce device insertion loss, and improve the overall performance of the filter. BRIEF DESCRIPTION OF DRAWINGS

[0026] Fig. 1 is a step flow block diagram of the transversely excited bulk acoustic wave filter manufacturing method provided by the embodiment of the present application;

[0027] Fig. 2 is a process flow diagram of the transversely excited bulk acoustic wave filter manufacturing method provided by the embodiment of the present application. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below by combining with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0029] Please refer to Fig. 1 and Fig. 2, Fig. 1 is a step flow block diagram of the transversely excited bulk acoustic wave filter manufacturing method provided by the embodiment of the present application, and Fig. 2 is a process flow diagram of the transversely excited bulk acoustic wave filter manufacturing method provided by the embodiment of the present application. The manufacturing method comprises the following steps:

[0030] S1, providing a silicon-based substrate material 1 and a photosensitive glass 2;

[0031] S2, bonding the lower surface of the photosensitive glass 2 to the upper surface of the silicon-based substrate material 1 through a bonding process;

[0032] S3, mechanically thinning and polishing the upper surface of the photosensitive glass 2;

[0033] S4, exposing and annealing the photosensitive glass 2 to crystallize a part of the photosensitive glass 2 to form a crystallized glass 3;

[0034] S5, preparing a piezoelectric material 4 on the upper surface of the photosensitive glass 2;

[0035] S6, growing a metal on the upper surface of the piezoelectric material 4 and forming an interdigital transducer 5 by a patterning process;

[0036] S7, etching the piezoelectric material 4 to form an etching through hole 6 penetrating through the piezoelectric material and connecting the crystallized glass 3 with the outside;

[0037] S8, releasing the sacrificial layer of the crystallized glass 3 through the etching through hole 6 to obtain a series-parallel resonator with a cavity 7;

[0038] S9, connecting a plurality of the series-parallel resonators according to a preset electrical rule to obtain a transverse excitation bulk acoustic wave filter.

[0039] The bonding process in step S2 uses an adhesive material which is at least one of silicon oxide and aluminum oxide. The silicon-based substrate 1 and the photosensitive glass 2 are bonded as a whole by the bonding process with the adhesive material as an intermediate layer, which supports the piezoelectric material 4.

[0040] In step S4, the thickness of the crystallized glass 3 is controlled to be 0.1-10um by controlling the exposure and annealing time of the photosensitive glass 2. At the same time, after the exposure and annealing process, the photomask pattern is transferred to the substrate of the photosensitive glass 2, and the pattern can be obtained in any shape according to the requirement.

[0041] The method for preparing the piezoelectric material 4 on the upper surface of the photosensitive glass 2 in step S5 is magnetron sputtering or a bonding process. When the piezoelectric material 4 is prepared based on the bonding process, the adhesive material is at least one of silicon oxide and aluminum oxide.

[0042] In step S6, the method for growing the metal includes at least one of magnetron sputtering and chemical vapor deposition, and the patterning process includes at least one of photolithography stripping and photolithography etching.

[0043] In step S7, the method for etching the piezoelectric material 4 includes at least one of gas etching and liquid etching.

[0044] In step S8, since the crystallized glass and the uncrystallized photosensitive glass have a high etching selectivity, according to the shape on the substrate, the crystallized glass can be simply and selectively etched away to obtain a cavity structure corresponding to the shape of the substrate.

[0045] The preset electrical rule in step S9 is a rule for connecting different resonators to realize certain filter characteristics, which follows the existing filter principle, and according to different use scenarios, the electrical performance of the finally obtained transversely excited bulk acoustic wave filter is also different. The embodiment of the present application does not make specific limitation on how to connect the resonators, and can be designed according to the needs in the implementation process.

[0046] The piezoelectric material 4 is lithium tantalate single crystal or lithium niobate single crystal, and the thickness of the piezoelectric material is 0.1-1um.

[0047] The metal constituting the interdigital transducer 5 is at least one of gold, aluminum, copper, silver and titanium, and the thickness of the interdigital transducer 5 is 0.1um to 20 times the thickness of the piezoelectric material. When the interdigital transducer is realized based on multiple metals, the metal used is a synthetic metal.

[0048] The embodiment of the present application has the beneficial effects that a manufacturing method of a transversely excited bulk acoustic wave filter is realized by using the excellent characteristics of silicon and photosensitive glass respectively, the photosensitive glass is exposed and annealed to obtain a crystallized glass as a sacrifice layer, and the pattern transfer is completed, which does not involve cavity photolithography, etching and plating, reduces the process steps, can reduce the difficulty and cost, improves the yield and structural stability of the filter; at the same time, the crystallized glass and the uncrystallized photosensitive glass have high etching selectivity and extremely low parasitic resistance and capacitance, the cavity etching can be simply and accurately controlled to obtain an ideal cavity structure, and the device insertion loss can be reduced and the overall performance of the filter is improved.

[0049] The embodiment of the present application also provides a radio frequency module including the transversely excited bulk acoustic wave filter manufactured by the manufacturing method of the transversely excited bulk acoustic wave filter. It can be understood that the manufacturing method of the transversely excited bulk acoustic wave filter proposed based on the embodiment of the present application generates a transversely excited bulk acoustic wave filter with an ideal cavity structure by using the excellent characteristics of silicon and photosensitive glass respectively, the radio frequency module realized based on the structure can reduce the device insertion loss, and the overall performance of the filter is improved, so that the radio frequency module has the advantages of high frequency, large bandwidth and low loss.

[0050] It should be noted that in this document, the terms "comprising", "including", or any other variant thereof are intended to cover non-exclusive inclusions, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such a process, method, article or device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of another identical element in the process, method, article or device including the element.

[0051] The embodiments of the present application are described above with reference to the accompanying drawings, and the disclosed are only the preferred embodiments of the present application, but the present application is not limited to the above-mentioned specific embodiments, and the above-mentioned specific embodiments are only illustrative, but not restrictive, and those skilled in the art can make many equivalent changes without departing from the spirit of the present application and the scope of the claims, and all the equivalent changes are within the protection scope of the present application.

Claims

1. A method of fabricating a transversely excited bulk acoustic wave filter, characterized by, The manufacturing method comprises the following steps: S1, providing a silicon-based substrate material and a photosensitive glass; S2, bonding the lower surface of the photosensitive glass with the upper surface of the silicon-based substrate material through a bonding process; S3, mechanically thinning and polishing the upper surface of the photosensitive glass; S4, exposing and annealing the photosensitive glass to crystallize a part of the photosensitive glass into a crystallized glass; S5, preparing a piezoelectric material on the upper surface of the photosensitive glass; S6, growing a metal on the upper surface of the piezoelectric material and forming an interdigital transducer through a patterning process; S7, etching the piezoelectric material to form an etching via hole penetrating through the piezoelectric material and connecting the crystallized glass with the outside; S8, releasing a sacrificial layer of the crystallized glass through the etching via hole to obtain a series-parallel resonator with a cavity; S9, connecting a plurality of the series-parallel resonators according to a preset electrical rule to obtain a lateral excitation bulk acoustic wave filter.

2. The method of manufacturing a lateral excitation bulk acoustic wave filter according to claim 1, wherein The bonding process in step S2 uses an adhesive material which is at least one of silicon oxide and aluminum oxide.

3. The method of manufacturing a lateral excitation bulk acoustic wave filter according to claim 1, wherein In step S4, the thickness of the crystallized glass is controlled to be 0.1-10 um by controlling the exposure and annealing time of the photosensitive glass.

4. The method of manufacturing a lateral excitation bulk acoustic wave filter according to Claim 1, wherein In step S5, the method for preparing the piezoelectric material on the upper surface of the photosensitive glass is magnetron sputtering or a bonding process.

5. The method of manufacturing a lateral excitation bulk acoustic wave filter according to claim 1, wherein In step S6, the method for growing the metal includes at least one of magnetron sputtering and chemical vapor deposition, and the patterning process includes at least one of photolithography stripping and photolithography etching.

6. The method of manufacturing a lateral excitation bulk acoustic wave filter according to Claim 1, wherein In step S7, the method for etching the piezoelectric material includes at least one of gas etching and liquid etching.

7. The method of manufacturing a lateral excitation bulk acoustic wave filter according to Claim 1, wherein The piezoelectric material is lithium tantalate single crystal or lithium niobate single crystal, and the thickness of the piezoelectric material is 0.1-1 um.

8. The method of manufacturing a lateral excitation bulk acoustic wave filter according to Claim 1, wherein The metal constituting the interdigital transducer is at least one of gold, aluminum, copper, silver and titanium, and the thickness of the interdigital transducer is 0.1 um to 20 times the thickness of the piezoelectric material.

9. A radio frequency module, characterized by The lateral excitation bulk acoustic wave filter manufactured by the manufacturing method of any one of claims 1-8. The lateral excitation bulk acoustic wave filter manufactured by the manufacturing method of any one of claims 1-8.

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