Micro-coaxial transmission line and method for manufacturing micro-coaxial transmission line

Abstract

The present invention provides a micro-coaxial transmission line and a method for manufacturing the same, belonging to the field of micro-coaxial technology. The transmission line comprises a substrate and a transmission line body, the transmission line body being disposed on the substrate. The transmission line body comprises an inner conductor and an outer conductor, the outer conductor being disposed on the periphery of the inner conductor, and an air cavity being formed between the inner and outer conductors. A support anchor structure is provided on the substrate, the bottom of the support anchor structure being connected to the substrate and the top of the support anchor structure being connected to the inner conductor. The support anchor structure of the transmission line can be directly generated during the manufacturing process of the inner and outer conductors, thereby eliminating the need to design specialized materials to support the micro-coaxial inner conductor. This method can reduce the difficulty of implementing the micro-coaxial process and avoid the complex control steps involved in manufacturing the inner conductor support structure, thereby improving the manufacturing efficiency and reducing the manufacturing cost of the micro-coaxial transmission line.

Description

Technical Field

[0001] The present invention relates to the field of micro-coaxial technology, and in particular to a micro-coaxial transmission line and a method for manufacturing the micro-coaxial transmission line. Background Art

[0002] As a basic circuit structure of radio frequency devices manufactured using MEMS (micro-electromechanical systems) technology, micro-coaxial transmission lines have received widespread attention in the field of millimeter-wave radio frequency technology in recent years. Micro-coaxial transmission lines have many advantages such as small size, light weight, low loss, high isolation and good heat dissipation performance. These characteristics make micro-coaxial transmission lines show great potential in radio frequency applications. The prior art discloses a variety of methods for preparing micro-coaxial transmission line structures. These methods basically use thick-resin photolithography, electroplating, flattening and other micro-process cycle processing steps for production. The common feature of these process steps is that they all require the use of a special inner conductor support material structure manufacturing process to realize the suspended micro-coaxial inner conductor.

[0003] These processes increase the difficulty of manufacturing micro-coaxial transmission lines, and the manufacturing process requires precise control of the processing process of the support structure itself to ensure that the support structure is not damaged during the development of the sacrificial layer photoresist and the subsequent release of the sacrificial layer. In addition, in order to be compatible with the thick resist photolithography process of the main structure, the photolithography process of the polymer and other materials used as the support structure must be complexly controlled, which undoubtedly further increases the complexity and technical difficulty of the preparation process.

[0004] In summary, while existing micro-coaxial transmission line fabrication technologies meet the needs of RF applications to a certain extent, their complex process and high technical difficulty limit their wider application. Therefore, it is necessary to improve existing micro-coaxial transmission line fabrication technologies to overcome the shortcomings of existing technologies. Summary of the Invention

[0005] In order to overcome the problems existing in the related art, one of the purposes of the present invention is to provide a micro-coaxial transmission line, which supports the inner conductor through a support anchor structure on the substrate. The support anchor structure can be directly generated during the manufacturing process of the inner conductor and the outer conductor. Therefore, there is no need to design special materials to support the micro-coaxial inner conductor. It can meet the support requirements of the inner conductor while reducing the manufacturing difficulty and manufacturing cost of the transmission line.

[0006] A micro-coaxial transmission line comprises a substrate and a transmission line body, wherein the transmission line body is disposed on the substrate, the transmission line body comprises an inner conductor and an outer conductor, the outer conductor is disposed around the inner conductor, and an air cavity is formed between the inner conductor and the outer conductor;

[0007] A support anchor structure is provided on the substrate, wherein the bottom of the support anchor structure is connected to the substrate and the top of the support anchor structure is connected to the inner conductor.

[0008] In a preferred technical solution of the present invention, along the length direction of the transmission line body, at least one support anchor structure is provided at each end of the transmission line body.

[0009] In a preferred technical solution of the present invention, the cross-section of the support anchor structure is circular, elliptical or polygonal, and the size of the cross-section of the support anchor structure is 2500 square microns to 40000 square microns.

[0010] A second object of the present invention is to provide a method for manufacturing a micro-coaxial transmission line, the method being used to manufacture the micro-coaxial transmission line as described above, the manufacturing method comprising:

[0011] Designing support anchor structures at both ends of the micro-coaxial transmission line, wherein the support anchor structures are used to support the inner conductor of the micro-coaxial transmission line;

[0012] Obtaining a wafer, and processing it through insulating layer preparation, seed layer preparation, thick resist photolithography, electroplating, and wafer planarization to obtain a micro-coaxial transmission line with a support anchor structure;

[0013] The sacrificial layer of the micro-coaxial transmission line containing the support anchor structure is removed, so that the support anchor structure and the inner conductor are electrically disconnected from the outer conductor, thereby obtaining a micro-coaxial structure in which the inner conductor is supported by the support anchor structure.

[0014] In a preferred technical solution of the present invention, the steps of obtaining a wafer, preparing an insulating layer, preparing a seed layer, performing thick resist photolithography, electroplating, and wafer planarization to obtain a micro-coaxial transmission line having a support anchor structure include:

[0015] Insulating layer preparation: An insulating oxide layer is grown on the wafer surface by thermal oxidation;

[0016] Seed layer preparation: magnetron sputtering method, sputtering growth adhesion layer on the surface of the wafer with oxide layer, and sputtering a conductive seed layer on the adhesion layer;

[0017] Thick resist photolithography: Coating photoresist on the surface of the conductive seed layer and performing the first layer of photolithography based on the designed structure of the micro-coaxial transmission line to form a master pattern of the bottom surface of the micro-coaxial outer conductor and the support anchor point of the inner conductor on the substrate; curing, exposing and developing the photoresist to obtain a microstructure photolithography pattern;

[0018] Electroplating: Electroplating copper metal on the wafer with microstructure photolithography pattern;

[0019] Wafer planarization: Using the wafer planarization process, the thickness of the metal copper and photoresist on the wafer surface is controlled to the target thickness, thereby obtaining the first layer structure of the micro-coaxial transmission line containing the support anchor structure;

[0020] In a preferred technical solution of the present invention, after obtaining the first layer structure of the micro-coaxial transmission line containing the support anchor structure, the method further includes:

[0021] Repeating thick resist photolithography, electroplating and wafer planarization processes, a mask plate is used to prepare the sidewalls of the second layer structure of the micro-coaxial transmission line and the support anchor structure of the inner conductor on the first layer structure of the micro-coaxial transmission line.

[0022] In a preferred technical solution of the present invention, the seed layer preparation, thick resist photolithography, electroplating and wafer planarization processes are repeated, and a mask plate is used to prepare several layers of structures above the second layer structure of the micro-coaxial transmission line, as well as the outer conductor cover plate of the micro-coaxial transmission line, on the second layer structure of the micro-coaxial transmission line, to obtain a complete micro-coaxial transmission line structure.

[0023] In a preferred technical solution of the present invention, during the preparation of the insulating layer, the thickness of the oxidized insulating layer is greater than 1 μm;

[0024] During the seed layer preparation process, the adhesion layer is a metal titanium adhesion layer with a thickness of 20nm-30nm, and the conductive seed layer is a metal copper conductive seed layer with a thickness of 300nm-2000nm;

[0025] Between the preparation of the insulating layer and the preparation of the seed layer, the following steps are also included:

[0026] Wafer cleaning: The wafer with the oxide insulating layer is cleaned in 98% concentrated sulfuric acid for 15 minutes, then in 60°C hot deionized water, and then in cold deionized water, and then dried in an oven at 110°C-120°C.

[0027] In a preferred technical solution of the present invention, during the thick resist photolithography process, a layer of photoresist with a thickness of 110 μm to 120 μm is spin-coated on the surface of the wafer;

[0028] During the electroplating process, direct current or pulse electroplating is used; during the electroplating process, the plating solution temperature is controlled within the range of 20-30°C, and any of the plating solution circulation, cathode swing, and rotary electroplating methods are used to ensure uniform thickness of the electroplated copper;

[0029] During the wafer flattening process, mechanical polishing is first used to grind the metal copper and photoresist on the wafer surface; when the difference between the thickness of the metal copper and photoresist on the wafer surface and the target thickness is 3μm-8μm, chemical mechanical polishing is used to further flatten the wafer until the thickness of the metal copper and photoresist on the wafer surface reaches the target thickness.

[0030] In a preferred technical solution of the present invention, the sacrificial layer of the micro-coaxial transmission line containing the support anchor structure is removed, so that the support anchor structure and the inner conductor are electrically disconnected from the outer conductor, thereby obtaining a micro-coaxial structure in which the inner conductor is supported by the support anchor structure, comprising:

[0031] The micro-coaxial transmission line containing the support anchor structure is immersed in a debonding solvent to remove the sacrificial layer; wherein, during the immersion process, the temperature of the debonding solvent is greater than 70° C. and the immersion time is greater than 3 hours;

[0032] After removing the sacrificial layer, the seed layer inside the micro-coaxial structure and the wafer is removed by etching with a dilute nitric acid solution having a volume fraction of 5%. The adhesion layer is removed by etching with a hydrofluoric acid solution having a volume fraction of 3%.

[0033] The beneficial effects of the present invention are:

[0034] The present invention provides a micro-coaxial transmission line, comprising a substrate and a transmission line body, the transmission line body being disposed on the substrate and comprising an inner conductor and an outer conductor, the outer conductor being disposed around the inner conductor, and an air cavity being formed between the inner and outer conductors. A support anchor structure is disposed on the substrate, the support anchor structure being connected to the substrate at its bottom and to the inner conductor at its top. By integrating the support anchor structure on the substrate, the support anchor structure can be directly generated during the manufacturing process of the inner and outer conductors, thereby eliminating the need to design specialized materials to support the micro-coaxial inner conductor. This reduces the need for manufacturing additional support structures, simplifies the manufacturing process, and helps reduce production costs. Furthermore, the support anchor structure enhances mechanical support for the inner conductor, improving the overall structural stability of the micro-coaxial transmission line.

[0035] The present application also provides a method for manufacturing a micro-coaxial transmission line. The method comprises: designing support anchor structures at both ends of the micro-coaxial transmission line, the support anchor structures being used to support the inner conductor of the micro-coaxial transmission line; obtaining a wafer, and processing the wafer through insulating layer preparation, seed layer preparation, thick resist photolithography, electroplating, and wafer planarization to obtain the micro-coaxial transmission line containing the support anchor structures; and removing the sacrificial layer of the micro-coaxial transmission line containing the support anchor structures, thereby disconnecting the support anchor structures and the inner conductor from the outer conductor, thereby obtaining a micro-coaxial structure in which the inner conductor is supported by the support anchor structures. During the manufacturing process, by designing support anchor structures at both ends of the micro-coaxial transmission line, the method eliminates the step of using specialized support materials to support the inner conductor, which is required in traditional manufacturing processes. This reduces the number of manufacturing steps and simplifies the entire process. Since no specialized materials are required to support the micro-coaxial inner conductor, the method eliminates the complex photolithography process required to control the polymer or other materials used as the support structure, as is required in the prior art. This effectively reduces the difficulty of implementing the micro-coaxial process, reduces material and process costs, and makes the manufacture of micro-coaxial transmission lines more economical and efficient. In addition, during the production process, the size and position of the support anchor points can be flexibly adjusted to meet the requirements of different micro-coaxial transmission lines, thereby improving the flexibility and adaptability of the design. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Reference numerals:

[0037] 1. Substrate; 2. Support anchor structure; 3. Inner conductor; 4. Outer conductor; 5. Cavity; 6. Sacrificial layer; 7. Port anchor; 8. Micro-coaxial side wall; 9. Outer conductor cover. Description of the drawings:

[0039] Figure 1 is a flow chart of a method for manufacturing a micro-coaxial transmission line provided by an embodiment of the present invention;

[0040] Figure 2 This is a process flow chart for obtaining a micro-coaxial transmission line having a support anchor structure provided by an embodiment of the present invention;

[0041] Figure 3 is a process flow chart of obtaining a micro-coaxial structure in which an inner conductor is supported by a support anchor structure, provided by an embodiment of the present invention;

[0042] Figure 4 is a schematic structural diagram of a cross section of a micro-coaxial transmission line provided by an embodiment of the present invention;

[0043] Figure 5 Schematic diagram of the structure of a sacrificial layer formed after curing of the photoresist provided by an embodiment of the present invention on a substrate;

[0044] Figure 61 is a schematic structural diagram of a first layer structure of a micro-coaxial transmission line including a support anchor structure provided by an embodiment of the present invention;

[0045] Figure 7 1 is a schematic structural diagram of a second layer structure of a micro-coaxial transmission line including a support anchor structure provided by an embodiment of the present invention;

[0046] Figure 8 1 is a schematic structural diagram of the third layer structure of a micro-coaxial transmission line including a support anchor structure provided by an embodiment of the present invention;

[0047] Figure 9 1 is a schematic structural diagram of a micro-coaxial transmission line including an outer conductor cover plate provided by an embodiment of the present invention;

[0048] Figure 10 is a schematic structural diagram of a micro-coaxial structure after removing a sacrificial layer provided by an embodiment of the present invention;

[0049] Figure 11 is a stereoscopic diagram of a micro-coaxial transmission line provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0050] The preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. Rather, these embodiments are provided to make the present invention more thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0051] Various methods for fabricating micro-coaxial transmission line structures are currently available. These methods generally employ a cyclical micro-processing process involving thick-resist photolithography, electroplating, and planarization. These processes all require specialized inner conductor support material structures to achieve a suspended micro-coaxial inner conductor.

[0052] These processes increase the difficulty of manufacturing micro-coaxial transmission lines, and the manufacturing process requires precise control of the processing process of the support structure itself to ensure that the support structure is not damaged during the development of the sacrificial layer photoresist and the subsequent release of the sacrificial layer. In addition, in order to be compatible with the thick resist photolithography process of the main structure, the photolithography process of the polymer and other materials used as the support structure must be complexly controlled, which undoubtedly further increases the complexity and technical difficulty of the preparation process.

[0053] Based on this, the present application provides a method for manufacturing a micro-coaxial transmission line.

[0054] Example 1

[0055] like Figures 1-10As shown, this embodiment provides a method for manufacturing a micro-coaxial transmission line, comprising:

[0056] S100, designing support anchor structures 2 at both ends of the micro-coaxial transmission line, wherein the support anchor structures 2 are used to support the inner conductor 3 of the micro-coaxial transmission line;

[0057] During the design process, electromagnetic simulation software such as Ansys HFSS and CST can be used to design the structure and electromagnetic functions of the required micro-coaxial transmission line. The software is used to determine the size and position of the anchor points in the designed structure, as well as the distance between the inner conductor 3 and the outer conductor 4 at the transmission line port. These factors ensure that the micro-coaxial electromagnetic function is met and that the support anchor structure 2 cannot be connected to the outer conductor 4.

[0058] S200, obtaining a wafer, and performing processes such as preparing an insulating layer, preparing a seed layer, thick resist photolithography, electroplating, and wafer planarization to obtain a micro-coaxial transmission line containing a support anchor structure 2;

[0059] The wafers in this application can be silicon wafers or wafers of other materials. For example, they can be compound semiconductor materials such as gallium arsenide (GaAs), indium phosphide (InP), silicon carbide (SiC), and gallium nitride (GaN); they can also be silicon-on-insulator (SOI) materials or other new materials.

[0060] Specifically, the obtained wafer is a silicon wafer, the resistance of the wafer is 1Ω / cm-10Ω / cm, the crystal orientation can be 100, 110 or 111, and the thickness is 500μm-700 microns.

[0061] The process of obtaining a wafer, preparing an insulating layer, preparing a seed layer, performing thick resist photolithography, electroplating, and wafer planarization to obtain a micro-coaxial transmission line containing a support anchor structure 2 includes:

[0062] S201, preparing an insulating layer: growing an oxidized insulating layer on the surface of the wafer by a thermal oxidation method; the oxidized insulating layer is used to isolate the inner conductor 3 and the substrate 1 to prevent current leakage; during the preparation of the insulating layer, the thickness of the oxidized insulating layer is greater than 1 μm;

[0063] S202, seed layer preparation: magnetron sputtering method, sputtering growth adhesion layer on the surface of the wafer with the oxide layer, and sputtering a conductive seed layer on the adhesion layer; the conductive seed layer provides a basis for the subsequent electroplating step;

[0064] The adhesion layer is a metal titanium adhesion layer with a thickness of 20 nm to 30 nm, and the conductive seed layer is a metal copper conductive seed layer with a thickness of 300 nm to 2000 nm.

[0065] S203, thick resist photolithography: coating the surface of the conductive seed layer with photoresist, and performing the first layer photolithography according to the design structure of the micro-coaxial transmission line to form a master pattern of the bottom surface of the micro-coaxial outer conductor 4 and the support anchor point of the inner conductor 3 on the substrate 1; curing, exposing, and developing the photoresist to obtain a microstructure photolithography pattern;

[0066] S204, electroplating: electroplating metal copper on the wafer with the microstructure photolithography pattern formed thereon; electroplating metal copper to increase the thickness and strength of the conductor;

[0067] S205. Wafer planarization: A wafer planarization process is used to control the thickness of the metal copper and photoresist on the wafer surface to a target thickness, thereby obtaining the first layer structure of the micro-coaxial transmission line containing the support anchor structure 2. Wafer planarization is to remove excess metal and photoresist through chemical mechanical polishing or other planarization techniques to ensure that the surface of the transmission line is flat.

[0068] S300 , removing the sacrificial layer 6 of the micro-coaxial transmission line containing the support anchor structure 2 , so that the support anchor structure 2 and the inner conductor 3 are electrically disconnected from the outer conductor 4 , thereby obtaining a micro-coaxial structure in which the inner conductor 3 is supported by the support anchor structure 2 .

[0069] In this step, a specific chemical solvent or physical method is used to remove the sacrificial layer 6 material used as a temporary support structure during the micro-coaxial transmission line manufacturing process. This step disconnects the support anchor structure 2 and the electrical connection between the inner conductor 3 and the outer conductor 4, completing the fabrication of the micro-coaxial transmission line.

[0070] The above-mentioned method for manufacturing a micro-coaxial transmission line, during the manufacturing process, eliminates the need for specialized support materials to support the inner conductor 3 required in the traditional manufacturing process by designing support anchor structures 2 at both ends of the micro-coaxial transmission line. This reduces the number of manufacturing steps and simplifies the entire process. Since there is no need to design specialized materials to support the micro-coaxial inner conductor 3, the complex control steps required in the photolithography process of materials such as polymers serving as the support structure are eliminated in the prior art. This effectively reduces the difficulty of implementing the micro-coaxial process, reduces material and process costs, and makes the manufacture of micro-coaxial transmission lines more economical and efficient. Furthermore, during the production process, the size and position of the support anchors can be flexibly adjusted to meet the requirements of different micro-coaxial transmission lines, thereby improving the flexibility and adaptability of the design.

[0071] Specifically, the micro-coaxial transmission line includes a substrate 1 , and the support anchor structure 2 is provided between the substrate 1 and the inner conductor 3 . The bottom of the support anchor structure 2 is connected to the substrate 1 , and the top is connected to the inner conductor 3 .

[0072] By providing the support anchor structure 2 between the substrate 1 and the inner conductor 3, the inner conductor 3 is effectively supported, which not only ensures the structural stability of the inner conductor 3, but also reduces the manufacturing difficulty of the micro-coaxial transmission line and improves the manufacturing efficiency.

[0073] In one embodiment, after obtaining the first layer structure of the micro-coaxial transmission line containing the support anchor structure 2, the method further includes:

[0074] Repeating thick resist photolithography, electroplating and wafer planarization processes, a mask is used to prepare the sidewall of the second layer structure of the micro-coaxial transmission line and the support anchor structure 2 of the inner conductor 3 on the first layer structure of the micro-coaxial transmission line.

[0075] Furthermore, the seed layer preparation, thick resist photolithography, electroplating and wafer planarization processes are repeated, and a mask plate is used to prepare several layers of structures above the second layer structure of the micro-coaxial transmission line, as well as the outer conductor 4 cover plate of the micro-coaxial transmission line, on the second layer structure of the micro-coaxial transmission line, to obtain a complete micro-coaxial transmission line structure.

[0076] The micro-coaxial structure of the present application is provided with multiple layers. In practical applications, the number of layers of the micro-coaxial structure can be adjusted according to actual needs, and the sizes of the inner conductor 3 and the outer conductor 4 can also be adjusted according to needs.

[0077] In a more specific embodiment, between the preparation of the insulating layer and the preparation of the seed layer, the method further comprises:

[0078] Wafer cleaning: The wafer with the oxide insulating layer is cleaned in 98% concentrated sulfuric acid for 15 minutes, then in 60°C hot deionized water, and then in cold deionized water, and then dried in an oven at 110°C-120°C.

[0079] By using 98% concentrated sulfuric acid for cleaning, organic contamination and other difficult-to-remove impurities on the wafer surface can be effectively removed, improving the cleanliness of the wafer. The cleaning steps of 60°C hot deionized water and cold deionized water can further ensure the cleanliness of the wafer surface and remove residual sulfuric acid and other contaminants. Through a drying treatment at 110°C-120°C, the moisture on the wafer surface can be completely removed, preventing problems caused by the presence of moisture in subsequent process steps. This step can effectively improve the cleanliness of the wafer, providing a good foundation for subsequent process steps, thereby improving the efficiency of the entire manufacturing process and product quality.

[0080] Furthermore, during the thick resist photolithography process, a layer of photoresist with a thickness of 110μm-120μm is spin-coated on the surface of the wafer; during the spin-coating process, the uniformity and consistency of the photoresist layer are ensured by adjusting the spin-coating speed and spin-coating time.

[0081] During the electroplating process, direct current or pulse electroplating is used; during the electroplating process, the plating solution temperature is controlled within the range of 20-30°C, and any of the plating solution circulation, cathode swing, and rotary electroplating methods are used to ensure uniform thickness of the electroplated copper;

[0082] During wafer planarization, mechanical polishing is first used to grind away the copper and photoresist on the wafer surface. When the difference between the copper and photoresist thicknesses and the target thickness is 3μm-8μm, chemical mechanical polishing (CMP) is used to further flatten the wafer until the copper and photoresist thicknesses reach the target. Mechanical polishing is used for initial wafer surface planarization, primarily to remove the copper and photoresist. During the polishing process, the material thickness on the wafer surface is monitored in real time. When the difference between the copper and photoresist thicknesses and the target thickness is reduced to 3μm to 8μm, CMP is switched to CMP.

[0083] During the chemical mechanical polishing stage, the wafer surface is finely flattened through the synergistic effect of chemical corrosion and mechanical friction.

[0084] Combining mechanical polishing and chemical mechanical polishing can not only achieve the purpose of quickly removing excess material, but also ensure the flatness and smoothness of the final wafer surface.

[0085] Furthermore, the sacrificial layer 6 of the micro-coaxial transmission line containing the support anchor structure 2 is removed, so that the support anchor structure 2 and the inner conductor 3 are electrically disconnected from the outer conductor 4, thereby obtaining a micro-coaxial structure in which the inner conductor 3 is supported by the support anchor structure 2, including:

[0086] S301. Soak the micro-coaxial transmission line containing the support anchor structure 2 in a debonding solvent to remove the sacrificial layer 6. During the soaking process, the temperature of the debonding solvent is greater than 70° C. and the soaking time is greater than 3 hours. This step can effectively dissolve and remove the sacrificial layer 6.

[0087] S301 , after removing the sacrificial layer 6 , using 5% by volume dilute nitric acid to etch away the seed layer inside the micro-coaxial structure and the wafer; using 3% by volume hydrofluoric acid solution to etch away the adhesion layer.

[0088] The treatment time of dilute nitric acid solution should be adjusted according to the actual situation to ensure that the seed layer is completely removed. Similarly, the treatment time of hydrofluoric acid solution should also be adjusted according to the actual needs until the adhesion layer is completely removed.

[0089] Finally, the micro-coaxial structure after the above treatment is thoroughly cleaned to remove the residual corrosive liquid and other impurities. After cleaning, the micro-coaxial structure is dried to obtain the final micro-coaxial structure with the inner conductor 3 supported by the support anchor structure 2.

[0090] The following is a detailed description of the method for manufacturing the micro-coaxial transmission line of the present application:

[0091] (1) Design a micro-coaxial transmission line containing a support anchor structure 2 and a support inner conductor 3. In this step, electromagnetic simulation software such as Ansys HFSS, CST, etc. can be used to design the structure and electromagnetic function of the required micro-coaxial transmission line.

[0092] In the direction of the inner conductor 3 of the micro-coaxial port, it can be seen that there is a support anchor structure 2 below the inner conductor 3 at the port. The upper end of the support anchor is connected to the lower end surface of the micro-coaxial inner conductor 3, and the lower end of the anchor is connected to the upper surface of the substrate 1. At the same time, anchors are arranged at both ends of the inner conductor 3 of the micro-coaxial transmission line port. The anchors form a support for the inner conductor 3, and the substrate 1 supports the support anchor to ensure the formation of a stable micro-coaxial inner conductor 3 suspended structure.

[0093] (2) A silicon wafer is selected, and a micro-coaxial transmission line containing a supporting anchor structure 2 and a supporting inner conductor 3 structure is realized through micro-processing methods such as insulating layer preparation, seed layer preparation, thick resist photolithography, electroplating, and wafer flattening.

[0094] (21) Preparation of insulating layer: A silicon wafer is selected, such as a low-resistance (1-10Ω / cm), 100-orientation, 6-inch, 500-μm-thick silicon wafer. A 1-μm-thick oxide insulating layer is prepared on the surface of the silicon wafer by thermal oxidation, such as a wet oxygen process, at 1000°C.

[0095] (22) Wafer cleaning: For silicon wafers with an oxide layer on the surface, clean them in 98% concentrated sulfuric acid for 15 minutes, then rinse them in 60°C hot deionized water, and then rinse them in cold deionized water. Then, dry the surface in an oven at 110°C. The temperature of the cold deionized water should be less than 30°C.

[0096] (23) Seed layer preparation: A 20 nm thick titanium adhesion layer was sputtered on the surface of the silicon wafer with an oxide layer by magnetron sputtering, and then a 300 nm thick copper conductive seed layer was sputtered on the adhesion layer.

[0097] (24) Thick photoresist lithography: A spin coater is used to spin coat a 110 μm thick photoresist on the surface of the conductive seed layer in S23. Commonly used photoresists include AZ125nXT, etc., and then through the steps of curing, baking, exposure, and development, a photoresist pattern including the bottom surface of the micro-coaxial outer conductor 4 and the support anchor point of the inner conductor 3 is obtained. Figure 5, which is a schematic diagram of the bottom surface and the end surface of the port of the formed first layer of micro-coaxial transmission line.

[0098] (25) Electroplating: The wafers with photolithographic patterns are electroplated with 110-120 μm thick copper using an electroplating machine. The thickness of the copper and photoresist on the wafer surface is then controlled to 100 μm by planarization. Common electroplating methods include direct current and pulse plating, and the plating bath temperature is controlled within the range of 20-30°C. During the electroplating process, plating bath circulation, cathode swing, and rotation can be used to assist in achieving a uniform copper plating thickness.

[0099] (26) Wafer planarization: Common planarization methods include mechanical polishing, which uses 9μm aluminum oxide abrasives between the wafer polishing surface and the cast iron grinding wheel at 40-100 rpm. When the thickness of the copper layer and photoresist on the wafer surface reaches 103-108μm, the wafer is further planarized by chemical mechanical polishing until the thickness of the copper layer and photoresist is controlled to 100μm. Figure 6 As shown, the bottom surface of the first layer of the micro-coaxial transmission line and the support anchor structure 2 of the port are formed after the planarization process.

[0100] (27): By repeating steps (24)-(26), a mask is used to prepare the sidewall of the second layer of the micro-coaxial transmission line and the inner conductor 3 supporting anchor structure 2. Figure 7 Shown is the anchor structure of the second-layer sidewall and port of the formed micro-coaxial transmission line.

[0101] (28): By repeating steps (23)-(26), the sidewall and inner conductor structure of the third layer of the micro coaxial transmission line are prepared using a mask. Figure 8 Shown are the third layer sidewalls and inner conductor 3 of the formed micro-coaxial transmission line.

[0102] (29): By repeating steps (23)-(26), a mask is used to prepare the sidewall of the fourth layer of the micro-coaxial transmission line and the top surface of the fifth layer of the micro-coaxial transmission line to form a complete micro-coaxial transmission line structure. Figure 9 The figure shows the complete structure of the formed micro-coaxial transmission line before removing the sacrificial layer 6.

[0103] (3): The entire prepared wafer structure is soaked in a degumming solvent. Common degumming solvents such as dimethylpyrrolidone are used. The degumming agent is heated to 70°C and the degumming time is controlled to be more than 3 hours. After removing the photoresist sacrificial layer 6, the inside of the micro-coaxial structure and the wafer seed layer are removed by etching with a dilute nitric acid solution with a volume fraction of 5%, and the titanium adhesion layer is removed by etching with a hydrofluoric acid solution with a volume fraction of 3%. Through the above treatment, the electrical connection between the metal inner conductor 3 and the fixed anchor point below it and the outer conductor 4 is disconnected, forming a micro-coaxial structure in which the inner conductor 3 is supported by the substrate 1 port anchor point 7. Figure 10 The micro-coaxial structure shown.

[0104] Example 2

[0105] This embodiment provides a micro-coaxial transmission line, which is manufactured using the above-mentioned method for manufacturing a micro-coaxial transmission line;

[0106] See also Figure 11 The micro-coaxial transmission line includes a substrate 1 and a transmission line body, wherein the transmission line body is arranged on the substrate 1, and the transmission line body includes an inner conductor 3 and an outer conductor 4, wherein the outer conductor 4 is arranged around the inner conductor 3, and an air cavity is formed between the inner conductor 3 and the outer conductor 4;

[0107] A support anchor structure 2 is provided on the substrate 1 . Along the length direction of the transmission line body, the support anchor structure 2 is provided at both ends of the transmission line body for supporting the inner conductor 3 .

[0108] The cross section of the support anchor structure is circular, elliptical or polygonal, and the size of the cross section of the support anchor structure is 2500 square microns to 40000 square microns.

[0109] In practical applications, the cross-sectional shape and size of the support anchor structure 2 can be adjusted according to specific application requirements to meet the requirements of miniaturized, high-performance transmission lines in different fields.

[0110] The micro-coaxial transmission line is directly connected to the substrate 1 and inner conductor 3 via the support anchor structure 2, providing more direct and stable support and enhancing the overall structural stability of the micro-coaxial transmission line. Furthermore, the specialized support materials required in traditional manufacturing processes are omitted, reducing material and process costs, making the manufacture of the micro-coaxial transmission line more economical and efficient.

[0111] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

[0112] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A micro-coaxial transmission line, characterized in that: The transmission line body comprises a substrate and a transmission line main body, wherein the transmission line main body is arranged on the substrate, the transmission line main body comprises an inner conductor and an outer conductor, the outer conductor is arranged around the inner conductor, an air cavity is formed between the inner conductor and the outer conductor, and both ends of the inner conductor extend out of the outer conductor and are exposed outside the outer conductor; A support anchor structure is provided on the substrate. Along the length direction of the transmission line body, the support anchor structure is provided at both ends of the transmission line body for supporting the inner conductor; the bottom of the support anchor structure is connected to the substrate, and the top is connected to the inner conductor.

2. The micro-coaxial transmission line according to claim 1, wherein: Along the length direction of the transmission line body, at least one support anchor structure is provided at each end of the transmission line body.

3. The micro-coaxial transmission line according to claim 1, wherein: The cross section of the support anchor structure is circular, elliptical or polygonal, and the size of the cross section of the support anchor structure is 2500 square microns to 40000 square microns.

4. A method for manufacturing a micro-coaxial transmission line, characterized in that: For manufacturing the micro-coaxial transmission line according to any one of claims 1 to 3, the manufacturing method comprises: Designing support anchor structures at both ends of the micro-coaxial transmission line, wherein the support anchor structures are used to support the inner conductor of the micro-coaxial transmission line; Obtaining a wafer, and processing it through insulating layer preparation, seed layer preparation, thick resist photolithography, electroplating, and wafer planarization to obtain a micro-coaxial transmission line with a support anchor structure; Removing the sacrificial layer of the micro-coaxial transmission line containing the support anchor structure, so that the support anchor structure and the inner conductor are electrically disconnected from the outer conductor, thereby obtaining a micro-coaxial structure in which the inner conductor is supported by the support anchor structure; The process of obtaining a wafer, preparing an insulating layer, preparing a seed layer, performing thick resist photolithography, electroplating, and wafer planarization to obtain a micro-coaxial transmission line having a support anchor structure includes: Insulating layer preparation: An insulating oxide layer is grown on the wafer surface by thermal oxidation; Seed layer preparation: magnetron sputtering method, sputtering growth adhesion layer on the surface of the wafer with oxide layer, and sputtering a conductive seed layer on the adhesion layer; Thick resist photolithography: Coating photoresist on the surface of the conductive seed layer and performing the first layer of photolithography based on the designed structure of the micro-coaxial transmission line to form a master pattern of the bottom surface of the micro-coaxial outer conductor and the support anchor point of the inner conductor on the substrate; curing, exposing and developing the photoresist to obtain a microstructure photolithography pattern; Electroplating: Electroplating copper metal on the wafer with microstructure photolithography pattern; Wafer planarization: Using the wafer planarization process, the thickness of the metal copper and photoresist on the wafer surface is controlled to the target thickness, and the first layer structure of the micro coaxial transmission line containing the support anchor structure is obtained.

5. The method for manufacturing a micro-coaxial transmission line according to claim 4, wherein: After obtaining the first layer structure of the micro-coaxial transmission line containing the support anchor structure, the method further includes: Repeating thick resist photolithography, electroplating and wafer planarization processes, a mask plate is used to prepare the sidewalls of the second layer structure of the micro-coaxial transmission line and the support anchor structure of the inner conductor on the first layer structure of the micro-coaxial transmission line.

6. The method for manufacturing a micro-coaxial transmission line according to claim 5, wherein: The seed layer preparation, thick resist photolithography, electroplating and wafer planarization processes are repeated. On the second layer structure of the micro-coaxial transmission line, a mask plate is used to prepare several layers of structures above the second layer structure of the micro-coaxial transmission line, as well as the outer conductor cover plate of the micro-coaxial transmission line, to obtain a complete micro-coaxial transmission line structure.

7. The method for manufacturing a micro-coaxial transmission line according to any one of claims 4 to 6, characterized in that: During the preparation of the insulating layer, the thickness of the oxidized insulating layer is greater than 1 μm; During the seed layer preparation process, the adhesion layer is a metal titanium adhesion layer with a thickness of 20nm-30nm, and the conductive seed layer is a metal copper conductive seed layer with a thickness of 300nm-2000nm; Between the preparation of the insulating layer and the preparation of the seed layer, the following steps are also included: Wafer cleaning: The wafer with the oxide insulating layer is cleaned in 98% concentrated sulfuric acid for 15 minutes, then in 60°C hot deionized water, and then in cold deionized water, and then dried in an oven at 110°C-120°C.

8. The method for manufacturing a micro-coaxial transmission line according to any one of claims 4 to 6, characterized in that: During thick resist lithography, a layer of photoresist 110μm-120μm thick is spin-coated on the wafer surface; During the electroplating process, direct current or pulse electroplating is used; during the electroplating process, the plating solution temperature is controlled within the range of 20-30°C, and any of the plating solution circulation, cathode swing, and rotary electroplating methods are used to ensure uniform thickness of the electroplated copper; During the wafer flattening process, mechanical polishing is first used to grind the metal copper and photoresist on the wafer surface; when the difference between the thickness of the metal copper and photoresist on the wafer surface and the target thickness is 3μm-8μm, chemical mechanical polishing is used to further flatten the wafer until the thickness of the metal copper and photoresist on the wafer surface reaches the target thickness.

9. The method for manufacturing a micro-coaxial transmission line according to any one of claims 4 to 6, wherein: The sacrificial layer of the micro-coaxial transmission line containing the support anchor structure is removed, so that the support anchor structure and the inner conductor are electrically disconnected from the outer conductor, thereby obtaining a micro-coaxial structure in which the inner conductor is supported by the support anchor structure, comprising: The micro-coaxial transmission line containing the support anchor structure is immersed in a debonding solvent to remove the sacrificial layer; wherein, during the immersion process, the temperature of the debonding solvent is greater than 70° C. and the immersion time is greater than 3 hours; After removing the sacrificial layer, the seed layer inside the micro-coaxial structure and the wafer is removed by etching with a dilute nitric acid solution having a volume fraction of 5%. The adhesion layer is removed by etching with a hydrofluoric acid solution having a volume fraction of 3%.

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