Preparation method of surface acoustic wave filter and surface acoustic wave filter

Abstract

The invention relates to the technical field of wireless communication, and provides a preparation method of a surface acoustic wave filter and the surface acoustic wave filter.The preparation method comprises the steps that S1, a substrate of the surface acoustic wave filter is obtained; s2, growing a plurality of metal electrodes and a protective layer on the front surface of the substrate, wherein the protective layer completely covers the plurality of metal electrodes; s3, presetting a soaking column area on the substrate, and spin-coating a layer of photoresist on the back surface of the substrate; s4, removing the photoresist in the soaking column region through exposure and development; s5, etching the soaking column region through dry etching to form a groove, and removing the residual photoresist on the substrate; s6, depositing an electroplating seed layer on the back surface of the substrate, and continuing to complete the copper electroplating process, so that the groove is filled with copper; and S7, grinding the back surface of the substrate until the back surface of the substrate is exposed, and reserving the soaking column formed in the groove to obtain the surface acoustic wave filter. The surface acoustic wave filter provided by the invention can effectively improve the thermal damage resistance of the device under the working condition of high input power.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless communication, and in particular to a preparation method of a surface acoustic wave filter and a surface acoustic wave filter. Background Art

[0002] The power handling of SAW filters is critical because it directly affects the performance stability and reliability of the filter under high signal strength conditions. In wireless communications, RF applications, and other high-frequency systems, the signal strength can be very high, and the filter needs to have sufficient power handling capabilities to ensure that it can operate normally without distortion in a strong signal environment. High power handling not only helps maintain the linearity of the output signal and avoid nonlinear distortion, but also effectively manages heat to prevent overheating from causing performance degradation or device damage.

[0003] The power capacity of existing SAW filters is also related to the long-term reliability and service life of the filters. High power handling capability can reduce the risk of failure under extreme conditions. When designing and selecting SAW filters, ensuring that their power capacity meets application requirements is a key factor in improving system performance and stability.

[0004] However, there are few options for improving the power capacity of commonly used surface acoustic wave filters. Usually, the only options are to replace the substrate with higher cost, more complex process and higher thermal conductivity; or to choose BAW devices (Bulk Acoustic Wave) to meet the design indicators of power capacity, which leads to an increase in the overall thermal conductivity of the substrate of the surface acoustic wave filter, and the cost and process of the substrate also increase accordingly. Summary of the invention

[0005] In view of the above shortcomings of the prior art, the present invention proposes a method for preparing a surface acoustic wave filter to solve the problems of high cost and poor heat loss resistance of the existing surface acoustic wave filter.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: In a first aspect, an embodiment of the present invention provides a method for preparing a surface acoustic wave filter, the method comprising the following steps: S1. Obtaining a substrate for making a surface acoustic wave filter; S2. growing a plurality of metal electrodes and a protective layer on the front surface of the substrate, wherein the protective layer completely covers the plurality of metal electrodes; S3, presetting a heat soaking column area on the substrate, and spin coating a layer of photoresist on the back side of the substrate; S4, removing the photoresist in the heat-soaking column area by exposure and development; S5, etching the soaking column region to form a groove by dry etching, and removing the remaining photoresist on the substrate; wherein the depth of the groove is 40% to 100% of the thickness of the substrate; S6, depositing an electroplating seed layer on the back side of the substrate, and continuing to complete the copper electroplating process to fill the groove; S7, grinding the back side of the substrate to expose the back side of the substrate, retaining the heat-sinking column formed in the groove, and obtaining the surface acoustic wave filter.

[0007] Preferably, in S1, the substrate is made of piezoelectric material or semiconductor wafer substrate material.

[0008] Preferably, the piezoelectric material is lithium tantalate or lithium niobate.

[0009] Preferably, the metal electrode is made of aluminum or aluminum-copper alloy.

[0010] Preferably, the protective layer is made of silicon dioxide or silicon nitride.

[0011] Preferably, in S3, the method for presetting the soaking column area comprises the following steps: Preset a plurality of resonators, and select a resonator with the largest failure rate among the plurality of resonators according to simulation, wherein the resonator is less than 1 / 2 of the total number of resonators on the surface acoustic wave filter; The heat-absorbing column area is obtained according to the position of the resonator.

[0012] In a second aspect, an embodiment of the present invention provides a surface acoustic wave filter, which is manufactured based on the above-mentioned surface acoustic wave filter manufacturing method, and the surface acoustic wave filter includes a substrate, a heat-dissipating column arranged in the substrate, a resonator arranged on the back side of the substrate and stacked and fixed on the heat-dissipating column, a plurality of metal electrodes arranged on the front side of the substrate, and a protective layer stacked on the front side of the substrate; the plurality of metal electrodes are spaced apart from each other, and the plurality of metal electrodes are electrically connected by wires, and the protective layer covers the plurality of metal electrodes.

[0013] Preferably, a perspective outline is preset on the back side of the substrate, and a projection of the outline in the direction of the heat-soaking column falls within the range of the heat-soaking column.

[0014] Preferably, the distance between the edge of the contour and the edge of the resonator is 10-20 um.

[0015] Compared with the related art, in an embodiment of the present invention, a substrate for making a surface acoustic wave filter is obtained; a plurality of metal electrodes and a protective layer are grown on the front side of the substrate, wherein the protective layer completely covers the plurality of metal electrodes; a heat spreader region is preset on the substrate, and a layer of photoresist is spin-coated on the back side of the substrate; the photoresist in the heat spreader region is removed by exposure and development; a groove is formed by dry etching the heat spreader region, and the remaining photoresist on the substrate is removed; an electroplating seed layer is deposited on the back side of the substrate, and a copper electroplating process is continued to fill the groove; the back side of the substrate is ground until the back side of the substrate is exposed, retaining the heat spreader formed in the groove, and a surface acoustic wave filter is obtained; by setting the heat spreader region, the device's resistance to thermal damage under high input power conditions is effectively improved without significantly increasing material costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be described in detail below in conjunction with the accompanying drawings. The above and other aspects of the present invention will become clearer and easier to understand through the detailed description made in conjunction with the following drawings. In the accompanying drawings: Figure 1 A flow chart of a method for preparing a surface acoustic wave filter provided in Embodiment 1 of the present invention; Figure 2 A specific process principle diagram of the method for preparing a surface acoustic wave filter provided in the first embodiment of the present invention; Figure 3 A schematic diagram of the three-dimensional structure of a surface acoustic wave filter provided in Embodiment 2 of the present invention; Figure 4 A schematic diagram of the internal structure of a surface acoustic wave filter provided in Embodiment 2 of the present invention; Figure 5 A top view of a surface acoustic wave filter provided in Embodiment 2 of the present invention; Figure 6 A schematic diagram of the maximum temperature at the center of the resonator of the surface acoustic wave filter provided in the second embodiment of the present invention without a heat-saturating column; Figure 7 This is a schematic diagram of the maximum temperature at the center of the resonator of the surface acoustic wave filter provided in the second embodiment of the present invention under the condition of a heat-saturating column.

[0017] Among them, 100, surface acoustic wave filter, 1, substrate, 2, protective layer, 3, metal electrode, 4, heat sink, 5, seed layer, 6, groove, 7, photoresist, 8, outline, 9, wire. DETAILED DESCRIPTION

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of the present application; the terms used in the specification of the application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "including" and "having" and any variations thereof in the specification and claims of the present application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of the present application or the above-mentioned drawings are used to distinguish different objects, not to describe a specific order.

[0019] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] Embodiment 1 See also Figure 1-Figure 2 As shown, an embodiment of the present invention provides a method for preparing a surface acoustic wave filter, and the preparation method comprises the following steps: S1. Obtain a substrate 1 for making a surface acoustic wave filter.

[0022] S2. Growing a plurality of metal electrodes 3 and a protective layer 2 on the front surface of the substrate 1, wherein the protective layer 2 completely covers the plurality of metal electrodes 3. Electrical connection is achieved through the metal electrodes 3, and the protective layer 2 is used to protect the metal electrodes 3 and increase the service life of the metal electrodes 3.

[0023] S3 , presetting a heat-sinking column area on the substrate 1 , and spin-coating a layer of photoresist 7 on the back side of the substrate 1 .

[0024] S4, by exposure and development, remove the photoresist 7 in the heat column area. The chip design pattern is accurately transferred to the silicon wafer or other substrate through photochemical reaction. The photoresist 7 transfers the designed circuit pattern to the surface of the semiconductor wafer through the photolithography process, thereby realizing high-precision chip manufacturing.

[0025] S5, etching the heat-sinking column region to form a groove 6 by dry etching, and removing the remaining photoresist 7 on the substrate 1; wherein the depth of the groove 6 is 40% to 100% of the thickness of the substrate 1.

[0026] S6, depositing an electroplating seed layer 5 on the back side of the substrate 1, and continuing the copper electroplating process to fill the groove 6. The seed layer 5 can be Au (gold) or the like, which has good conductive properties.

[0027] S7, grinding the back side of the substrate 1 until the back side of the substrate 1 is exposed, retaining the heat-sinking column 4 formed in the groove 6, and obtaining the surface acoustic wave filter.

[0028] Specifically, a substrate 1 for making a surface acoustic wave filter is obtained; a plurality of metal electrodes 3 and a protective layer 2 are grown on the front side of the substrate 1, wherein the protective layer 2 completely covers the plurality of metal electrodes 3; a heat-sinking column region is preset on the substrate 1, and a layer of photoresist 7 is spin-coated on the back side of the substrate 1; the photoresist 7 in the heat-sinking column region is removed by exposure and development; a groove 6 is formed by dry etching in the heat-sinking column region, and the remaining photoresist 7 on the substrate 1 is removed; an electroplating seed layer 5 is deposited on the back side of the substrate 1, and a copper electroplating process is continued to be completed so that the groove 6 is filled with copper; the back side of the substrate 1 is ground until the back side of the substrate 1 is exposed, and the heat-sinking column 4 formed in the groove 6 is retained to obtain a surface acoustic wave filter; by setting the heat-sinking column region, the device's resistance to thermal damage under high input power conditions is effectively improved without significantly increasing material costs.

[0029] In this embodiment, in S1, the substrate 1 is made of piezoelectric material or semiconductor wafer substrate 1 material.

[0030] In this embodiment, the piezoelectric material is lithium tantalate or lithium niobate.

[0031] In this embodiment, the metal electrode 3 is made of aluminum or aluminum-copper alloy material, which has good electrical conductivity.

[0032] In this embodiment, the protective layer 2 is made of silicon dioxide or silicon nitride. The protective layer 2 is usually made of silicon dioxide or silicon nitride that comes with the filter wafer when it leaves the factory, and has high structural strength.

[0033] In this embodiment, in S3, the method for presetting the soaking column area includes the following steps: A plurality of resonators are preset, and according to simulation, a resonator with the largest failure rate among the plurality of resonators is selected, and the resonator is less than 1 / 2 of the total number of resonators on the surface acoustic wave filter; and the heat-sinking column area is obtained according to the position of the resonator. By manufacturing the structure of the heat-sinking column 4 on the heat-sinking column area, the heat dissipation effect is good.

[0034] Embodiment 2 See also Figure 3-Figure 5 As shown, an embodiment of the present invention provides a surface acoustic wave filter 100, which is manufactured based on the above-mentioned surface acoustic wave filter manufacturing method, and the surface acoustic wave filter 100 includes a substrate 1, a heat-sinking column 4 arranged in the substrate 1, a resonator R1 arranged on the back of the substrate 1 and stacked and fixed on the heat-sinking column 4, a plurality of metal electrodes 3 arranged on the front of the substrate 1, and a protective layer 2 stacked on the front of the substrate 1; the plurality of metal electrodes 3 are spaced apart from each other, and the plurality of metal electrodes 3 are electrically connected through a wire 9, and the protective layer 2 covers the plurality of metal electrodes 3. The substrate 1 is used to install and set the metal electrodes 3 and the protective layer 2, the protective layer 2 is used to protect the metal electrodes 3, and the heat-sinking column 4 is used to dissipate heat from the resonator R1, which can effectively improve the device's resistance to thermal damage under high input power conditions without significantly increasing material costs.

[0035] In this embodiment, a perspective outline 8 is preset on the back of the substrate 1, and the projection of the outline 8 toward the heat-saturating column 4 falls within the range of the heat-saturating column 4. This facilitates the installation of the resonator R1 on the heat-saturating column 4 and further dissipates heat when the resonator R1 is working.

[0036] In this embodiment, the distance between the edge of the contour 8 and the edge of the resonator R1 is 10-20 um.

[0037] In this embodiment, the wire 9 is used to electrically connect multiple metal electrodes 3 to each other, R1 is a resonator R1 that needs to be optimized for heat dissipation, and usually the heat-saturating column 4 is directly below the resonator R1. The black cube is the heat-saturating column 4, and the outline 8 is appropriately expanded by 10-20 μm based on the size of the upper resonator R1. Optionally, the wire 9 is a metal interconnection line to facilitate the electrical connection of multiple metal electrodes 3.

[0038] Among them, through the finite element simulation surface, when the heating power of the resonator R1 is 0.07W, Figure 6 As shown in FIG. 1 , the maximum center temperature of the resonator R1 is 65.380 degrees Celsius without the heat-saturating column 4. Figure 7 As shown, under the condition of having the heat-saturating column 4, the highest temperature is only 48.276 degrees Celsius. Therefore, the present invention effectively improves the thermal damage resistance of the device under high input power conditions without significantly increasing the material cost.

[0039] It should be noted that the various embodiments described above with reference to the accompanying drawings are only used to illustrate the present invention rather than to limit the scope of the present invention. Those skilled in the art should understand that any modification or equivalent substitution of the present invention without departing from the spirit and scope of the present invention should be included within the scope of the present invention. In addition, unless otherwise indicated by the context, words appearing in the singular include the plural form, and vice versa. In addition, unless otherwise specified, all or part of any embodiment may be used in combination with all or part of any other embodiment.

Claims

1. A method for preparing a surface acoustic wave filter, characterized in that: The preparation method comprises the following steps: S1. Obtaining a substrate for making a surface acoustic wave filter; S2. growing a plurality of metal electrodes and a protective layer on the front surface of the substrate, wherein the protective layer completely covers the plurality of metal electrodes; S3, presetting a heat soaking column area on the substrate, and spin coating a layer of photoresist on the back side of the substrate; S4, removing the photoresist in the heat-soaking column area by exposure and development; S5, etching the soaking column region to form a groove by dry etching, and removing the remaining photoresist on the substrate; wherein the depth of the groove is 40% to 100% of the thickness of the substrate; S6, depositing an electroplating seed layer on the back side of the substrate, and continuing to complete the copper electroplating process to fill the groove; S7, grinding the back side of the substrate until the back side of the substrate is exposed, retaining the heat-sinking column formed in the groove, and obtaining the surface acoustic wave filter.

2. The method for preparing a surface acoustic wave filter according to claim 1, characterized in that: In S1, the substrate is made of piezoelectric material or semiconductor wafer substrate material.

3. The method for preparing a surface acoustic wave filter according to claim 2, characterized in that: The piezoelectric material is lithium tantalate or lithium niobate.

4. The method for preparing a surface acoustic wave filter according to claim 1, characterized in that: The metal electrode is made of aluminum or aluminum-copper alloy.

5. The method for preparing a surface acoustic wave filter according to claim 1, characterized in that: The protective layer is made of silicon dioxide or silicon nitride.

6. The method for preparing a surface acoustic wave filter according to claim 1, characterized in that: In said S3, the method for presetting said heat soaking column area comprises the following steps; Preset a plurality of resonators, and select a resonator with the largest failure rate among the plurality of resonators according to simulation, wherein the resonator is less than 1 / 2 of the total number of resonators on the surface acoustic wave filter; The heat-absorbing column area is obtained according to the position of the resonator.

7. A surface acoustic wave filter, wherein the surface acoustic wave filter is prepared based on the preparation method of the surface acoustic wave filter according to any one of claims 1 to 6, characterized in that: The surface acoustic wave filter comprises a substrate, a heat-sinking column arranged in the substrate, a resonator arranged on the back side of the substrate and stacked and fixed on the heat-sinking column, a plurality of metal electrodes arranged on the front side of the substrate, and a protective layer stacked on the front side of the substrate; The plurality of metal electrodes are spaced apart from each other and are electrically connected via wires, and the protective layer covers the plurality of metal electrodes.

8. The surface acoustic wave filter according to claim 7, characterized in that A perspective outline is also preset on the back side of the substrate, and a projection of the outline in the direction of the heat-soaking column falls within the range of the heat-soaking column.

9. The surface acoustic wave filter according to claim 8, characterized in that The distance between the edge of the contour and the edge of the resonator is 10-20 um.

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