A method for fabricating microstructures using photolithography-electroplating-assembly processes

Abstract

This invention provides a method for fabricating microstructures using a photolithography-electroplating-assembly process, offering a novel manufacturing method for heterogeneous processing of various materials. The method includes: designing a microstructure based on material selection and layer height processing rules; forming the main body of the microstructure using a photolithography-electroplating process; wherein, during the formation of the main body of the microstructure, a reserved position for forming an assembly structure is also included, and the assembly structure is implanted into the reserved position; the thickness of the assembly structure is 90-100 μm; the cross-sectional area of ​​the assembly structure is 0.04 mm. 2 -400mm 2 .

Description

Technical Field

[0001] This invention relates to the field of microstructure fabrication technology, and in particular to a method for preparing microstructures using a photolithography-electroplating-assembly process. Background Technology

[0002] Microstructure fabrication technology is a commonly used device manufacturing technology in the field of MEMS (Micro-Electro-Mechanical Systems), often employing micro- and nano-fabrication processes from the semiconductor industry. These processes include thin film growth, photolithography, etching, electroplating, laser processing, wet etching, and bonding. Since MEMS devices often possess certain three-dimensional structural features, representative microfabrication technologies, including LIGA, deep etching, and wafer bonding, have consistently been the primary methods for forming bulk structural features.

[0003] After years of technological accumulation and development, MEMS technology has developed a range of processing methods to form devices with relatively high aspect ratios through a combination of various fabrication techniques. However, regardless of whether etching or additive growth techniques are used, there are still relatively few methods that can form devices with a z-axis height greater than 1 mm. Among the many micro-nano fabrication processes, electroplating, as an electrochemical cold processing method, can form various types of metal structures. For example, a series of metals such as copper, nickel, gold, tin, silver, and zinc can be deposited and formed in aqueous solutions. However, the shapes of these electroplated metals cannot generally be controlled at will on the substrate; the desired patterns must be formed by using non-conductive pattern masking. Summary of the Invention

[0004] This invention provides a method for fabricating microstructures using a photolithography-electroplating-assembly process, offering a new manufacturing method for heterogeneous processing of various materials.

[0005] This invention provides a method for fabricating microstructures using a photolithography-electroplating-assembly process, comprising:

[0006] The microstructure is designed based on the material selection and layer height processing rules of the process.

[0007] The main body of the microstructure is formed by photolithography-electroplating based on the designed microstructure; wherein, the process of forming the main body of the microstructure also includes reserving positions for forming an assembly structure, and implanting the assembly structure into the reserved positions.

[0008] In one embodiment, the assembly structure is a heterogeneous structure; the assembly structure includes at least one of metal, ceramic and polymer.

[0009] In one embodiment, the main body portion is electroplated metal.

[0010] In one embodiment, inserting the assembly structure into the reserved location includes:

[0011] An automatic identification dispensing machine is used to automatically identify the reserved position of the assembly structure and move the nozzle of the dispensing gun to the center of the reserved position of the assembly structure to dispense glue.

[0012] An automatic identification die bonder is used to align the assembly structure with its center position. The assembly structure is then picked up by an automatic suction nozzle and moved to align with the center of the reserved position of the assembly structure on the wafer. The die bonder controls the reserved position or the suction nozzle to move in a direction perpendicular to the horizontal direction, so that the assembly structure is placed in the reserved position of the assembly structure after dispensing and comes into contact with the die bonder adhesive. The suction nozzle stops picking up the die, and the assembly structure is implanted into the reserved position of the assembly structure.

[0013] In one embodiment, the main body of the microstructure is formed by a photolithography-electroplating process based on the designed microstructure, including:

[0014] Step 01: Obtain a wafer as a substrate, sputter and grow an adhesion layer on the upper surface of the wafer based on the designed structure, and form a conductive seed layer on the adhesion layer;

[0015] Step 02: Coat the surface of the conductive seed layer with photoresist and perform photolithography based on the designed structure to obtain the photolithographic pattern of the microstructure;

[0016] Step 03: Electroplating a metal material onto the wafer on which the photolithographic pattern has been formed;

[0017] Step 04: After using a planarization process to control the thickness of the metal material and photoresist on the wafer surface to the target thickness, the first layer of the microstructure is obtained.

[0018] Step 05: Repeat steps 02 to 04 on the first layer structure until the main body of the microstructure is obtained.

[0019] In one embodiment, after the main body of the microstructure is formed by photolithography-electroplating based on the designed microstructure, the method further includes: removing the sacrificial layer of the main body to obtain the final microstructure.

[0020] In one implementation, removing the sacrificial layer of the main body portion to obtain the final microstructure includes:

[0021] The microstructure was soaked in a photoresist remover to remove the photoresist sacrificial layer.

[0022] After removing the sacrificial layer, dilute nitric acid etching is used to remove the seed layer inside the microstructure and the wafer.

[0023] The adhesion layer of the microstructure was removed by etching with hydrofluoric acid solution.

[0024] In one embodiment, after removing the sacrificial layer of the main body portion to obtain the final microstructure, the method further includes:

[0025] Remove substrate; or

[0026] The substrate is diced into wafers so that the entire wafer device can be formed into an independent device.

[0027] In one embodiment, the microstructure comprises a multilayer structure, wherein the height of each layer is 100 μm or 50 μm.

[0028] In one embodiment, forming the reserved positions for the assembly structure and implanting the assembly structure into the reserved positions includes: forming reserved positions for different levels of assembly structures during the formation of the main body of the microstructure, and implanting all assembly structures into the corresponding reserved positions; the thickness of the assembly structure is 90-100 μm; the cross-sectional area of ​​the assembly structure is 0.04 mm. 2 -400mm 2 .

[0029] As can be seen from the above technical solutions, the present invention has the following advantages:

[0030] This invention provides a method for fabricating microstructures using a photolithography-electroplating-assembly process. The method includes: designing a microstructure based on material selection and layer height processing rules; forming the main body of the microstructure using a photolithography-electroplating process based on the designed microstructure; and, during the formation of the main body of the microstructure, including reserving positions for forming an assembly structure and implanting the assembly structure into the reserved positions. This method, by employing auxiliary microfabrication processes on a wafer substrate and combining photolithography, electroplating, and assembly in sequence, can ultimately form microstructures combining heterogeneous materials such as metals with metals, metals with ceramics, metals with polymers, and metals with ceramics and polymers. This method is a novel microstructure formation process that, through wafer fabrication, can electroplat metal as the main structure, achieving heterogeneous processing combinations of metals with ceramics, polymers, and other materials, providing a new manufacturing approach for heterogeneous microstructures. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1This is a flowchart of a method for manufacturing a microstructure according to an embodiment of the present invention;

[0033] Figure 2 This is a flowchart of a method for manufacturing a microstructure according to another embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of the first layer structure of a microcoaxial transmission line manufactured using a microstructure manufacturing method according to an embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram of a two-layer photolithography master and a reserved position of a heterostructure for a micro-coaxial transmission line manufactured using a microstructure manufacturing method according to an embodiment of the present invention.

[0036] Figure 5 This is a schematic diagram of the adhesive for pre-assembled positions of a micro-coaxial transmission line manufactured using a microstructure manufacturing method according to an embodiment of the present invention;

[0037] Figure 6 This is a schematic diagram of a micro-coaxial transmission line pre-reserved position assembly ceramic structure and its bonding and curing completed using a microstructure manufacturing method according to an embodiment of the present invention;

[0038] Figure 7 This is a schematic diagram of a micro-coaxial transmission line electroplated with two layers of metal, completed using a microstructure manufacturing method according to an embodiment of the present invention;

[0039] Figure 8 This is a schematic diagram of the planarized two-layer metal structure of a micro-coaxial transmission line, which is manufactured using a microstructure manufacturing method according to an embodiment of the present invention.

[0040] Figure 9 This is a schematic diagram of a five-layer micro-coaxial transmission line structure manufactured using a microstructure manufacturing method according to an embodiment of the present invention;

[0041] Figure 10 This is a schematic diagram of the complete structure of a microcoaxial transmission line after removing the sacrificial layer using a microstructure manufacturing method according to an embodiment of the present invention;

[0042] Figure 11 This is a schematic diagram of the overall three-dimensional structure of a micro-coaxial transmission line prepared by a microstructure manufacturing method according to an embodiment of the present invention;

[0043] Figure 12 This is a schematic diagram of the internal structure of a microcoaxial transmission line prepared by a microstructure manufacturing method according to an embodiment of the present invention;

[0044] Figure 13 This is a schematic diagram of the first layer structure of a magnetic core micro inductor manufactured using a microstructure manufacturing method according to another embodiment of the present invention;

[0045] Figure 14 This is a schematic diagram of the two-layer photolithographic master and the reserved position of the heterostructure of the magnetic core micro inductor, which is manufactured using a microstructure manufacturing method according to another embodiment of the present invention.

[0046] Figure 15 This is a schematic diagram of the adhesive used to attach the pre-assembled positions of the magnetic core micro inductor, which is manufactured using a microstructure manufacturing method according to another embodiment of the present invention.

[0047] Figure 16 This is a schematic diagram of a ceramic structure assembled with a pre-reserved position for a magnetic core micro-inductor, and then bonded and cured using a microstructure manufacturing method provided in another embodiment of the present invention.

[0048] Figure 17 This is a schematic diagram of a two-layer metal electroplated structure of a magnetic core micro inductor manufactured using a microstructure manufacturing method according to another embodiment of the present invention;

[0049] Figure 18 This is a schematic diagram of the planarized two-layer metal structure of the magnetic core micro-inductor, which is manufactured using a microstructure manufacturing method according to another embodiment of the present invention.

[0050] Figure 19 This is a schematic diagram of a magnetic core micro-inductor assembly magnetic core structure and three-layer planarization completed using a microstructure manufacturing method provided in another embodiment of the present invention;

[0051] Figure 20 This is a schematic diagram of a five-layer structure of a magnetic core micro-inductor manufactured using a microstructure manufacturing method according to another embodiment of the present invention;

[0052] Figure 21 This is a schematic diagram of the complete structure of the magnetic core micro-inductor after removing the sacrificial layer using a microstructure manufacturing method provided in another embodiment of the present invention;

[0053] Figure 22 This is a schematic diagram of the overall three-dimensional structure of a magnetic core micro-inductor prepared by a microstructure manufacturing method according to another embodiment of the present invention.

[0054] Figure label:

[0055] 1. First electroplated metal layer; 2. Photoresist; 3. Support structure; 4. Second layer structure; 5. Third layer structure; 6. Fourth layer structure; 7. Fifth layer structure; 8. Wafer; 9. Sacrificial layer; 21. Substrate; 22. First sacrificial layer; 23. First electroplated metal layer; 24. Adhesive; 25. Ceramic structure; 26. Second electroplated metal layer; 27. Third electroplated metal layer; 28. Magnetic core structure; 29. ​​Fourth electroplated metal layer; 30. Fifth electroplated metal layer. Detailed Implementation

[0056] This invention provides a method for fabricating microstructures using a photolithography-electroplating-assembly process, offering a novel manufacturing method for heterogeneous processing of various materials.

[0057] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0058] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0059] In the several embodiments provided in this application, it should be understood that the methods, apparatuses, electronic devices, and storage media disclosed in this invention can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual couplings, direct couplings, or communication connections may be through some interfaces; indirect couplings or communication connections between devices or units may be electrical, mechanical, or other forms.

[0060] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0061] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0062] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a readable storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned readable storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0063] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0064] Example 1:

[0065] This embodiment provides a method for fabricating microstructures using a photolithography-electroplating-assembly process. Figure 1 This is a flowchart of a microstructure manufacturing method provided in an embodiment of the present invention; see reference. Figure 1 As shown, the method includes:

[0066] Step 01: Design the microstructure based on the material selection and layer height processing rules of the process.

[0067] Based on the material selection and layer height processing rules of this process, a microstructure with multi-layer mechanism is designed using software.

[0068] 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 microstructure. The electromagnetic simulation software is used to determine the size, location, and number of assembly structural pieces that need to be assembled within the designed structure.

[0069] Step 02: Based on the designed microstructure, the main body of the microstructure is formed by photolithography-electroplating process; wherein, the process of forming the main body of the microstructure also includes reserving positions for forming the assembly structure, and implanting the assembly structure into the reserved positions.

[0070] It is understood that during the process of forming the main body of the microstructure through photolithography-electroplating, the present invention can form reserved positions for the assembly structure at the target location according to the designed microstructure. Optionally, the microstructure includes a multi-layer structure, wherein there can be multiple reserved positions, and different reserved positions can be formed in the same layer or in different layer structures; the present invention does not limit this.

[0071] Optionally, the main body is electroplated metal.

[0072] Optionally, the assembly structure is a heterogeneous structure; the heterogeneous structure can be at least one of metal, ceramic and polymer.

[0073] This method employs auxiliary microfabrication processes and a sequential combination of photolithography, electroplating, and assembly to implant heterogeneous structures into the main body of a microstructure. This ultimately results in microstructures combining heterogeneous materials such as electroplated metals with metals, electroplated metals with ceramics, electroplated metals with polymers, and metals with ceramics and polymers. This method represents a novel microstructure formation process. Using wafer fabrication, it electroplats metals as the main structure and then assembles heterogeneous structures, enabling heterogeneous combinations of metals with ceramics, polymers, and other materials. This provides a new manufacturing approach for heterogeneous microstructures.

[0074] Example 2:

[0075] This embodiment provides a method for fabricating microstructures using a photolithography-electroplating-assembly process. The method for manufacturing the main structure includes:

[0076] (1) Obtain a wafer as a substrate, sputter an adhesion layer on the upper surface of the wafer based on the designed structure, and form a conductive seed layer on the adhesion layer.

[0077] Optionally, the wafer can be a silicon wafer or a wafer made of other materials, such as compound semiconductor materials like alumina, silicon carbide (SiC), and gallium arsenide (GaN); it can also be silicon-on-insulator (SOI) material or other novel materials. Specifically, the obtained wafer is a silicon wafer, generally with a resistivity of 1Ω / cm-10Ω / cm, crystal orientation 100 or 110, a thickness of 500μm-700μm, and an attached 1μm oxide insulating layer.

[0078] It is understood that the seed layer is usually prepared by magnetron sputtering, which sputters an adhesion layer on the wafer surface and then sputters a conductive seed layer on the adhesion layer. The conductive seed layer provides the basis for the subsequent electroplating steps. The adhesion layer can be a 20nm-30nm thick titanium adhesion layer, and the conductive seed layer can be a 300nm-2000nm thick copper conductive seed layer.

[0079] (2) Photoresist is coated on the surface of the conductive seed layer, and photolithography is performed based on the designed structure to obtain the photolithographic pattern of the microstructure.

[0080] Optionally, photoresist is coated on the surface of the conductive seed layer, and the bottom surface of the microstructure is formed on the substrate by the first layer of photolithography according to the design structure of the microstructure; the photoresist is cured, exposed and developed to obtain the microstructure photolithography pattern.

[0081] (3) Electroplating a metal material on the wafer on which the photolithographic pattern is formed.

[0082] Optionally, copper is electroplated onto the wafer on which the microstructure photolithography pattern is formed.

[0083] (4) After the thickness of the metal material and photoresist on the wafer surface is controlled to the target thickness by using a planarization process, the first layer structure of the microstructure is obtained.

[0084] Wafer planarization, as an auxiliary process, is mainly used to form a consistent plane between the metal structure and the photoresist or between the metal structure and the assembly structure. This layer adopts the wafer planarization process to control the thickness of the copper metal and photoresist on the wafer surface to the target thickness, thus obtaining the first layer structure of the microstructure. Wafer planarization is usually achieved by wafer mechanical polishing or chemical mechanical polishing technology.

[0085] (5) Repeat steps (2) to (4) on the first layer structure until the main part of the microstructure is obtained.

[0086] It should be noted in this step that the thick photoresist lithography, electroplating, and wafer planarization processes used in the repeated process are basically the same as those in the above steps. The only difference is that when the photolithography pattern changes, the corresponding process parameters are adjusted according to the change in the pattern area. For example, the change in the size of the electroplating pattern in different layers leads to the change in the electroplating current, which is easy to understand in the industry.

[0087] It should be explained that a multilayer structure of microstructures can be prepared by repeatedly performing steps (2) to (4). During the process of forming different structures of the main body of the microstructure through repeated steps (2) to (4), reserved positions for assembly structures at different levels can be formed simultaneously, and all assembly structures can be implanted into the corresponding reserved positions. It can be understood that the reserved positions of the assembly structures are not limited to any particular layer of the main body; that is, they can be formed during any repetition of steps (2) to (4). This invention does not limit the reserved positions of the assembly structures or the steps involved in forming these reserved positions.

[0088] The method for implanting the assembly structure into the reserved position is as follows.

[0089] Optionally, the assembly structure is a heterogeneous structure; the assembly structure includes at least one of metal, ceramic, and polymer. Implanting the assembly structure into a pre-defined location within the assembly structure can realize complex three-dimensional structures, heterogeneous material integration, or microstructures with higher aspect ratios.

[0090] Specifically, the step of inserting the assembly structure into the reserved position of the assembly structure includes:

[0091] An automatic identification dispensing machine is used to automatically identify the reserved position of the assembly structure and move the nozzle of the dispensing gun to the center of the reserved position of the assembly structure to dispense glue.

[0092] An automatic identification die bonder is used to align the assembly structure with its center position. The assembly structure is then picked up by an automatic suction nozzle and moved to align with the center of the reserved position of the assembly structure on the wafer. The die bonder controls the reserved position or the suction nozzle to move in a direction perpendicular to the horizontal direction, so that the assembly structure is placed in the reserved position of the assembly structure after dispensing and comes into contact with the die bonder adhesive. The suction nozzle stops picking up the die, and the assembly structure is implanted into the reserved position of the assembly structure.

[0093] The process of implanting the assembly structure into the reserved position includes: implanting all assembly structures into the corresponding reserved positions based on the design structure. It can be understood that the microstructure includes multiple structures that need to be assembled. The implantation process of the microstructure can be inserted into different hierarchical structures, and is not limited to a single implantation in step (2). That is, in the fabrication process of the microstructure, according to the design structure in step (1), it can be manufactured repeatedly and alternately in the manner of photolithography-electroplating-microassembly. This is significantly different from the traditional process that is continuously completed on a single substrate. This invention does not limit the order of the various steps.

[0094] Optionally, the height of each layer is 100 μm or 50 μm.

[0095] Optionally, the thickness of the assembly structure is in the range of 90-100 μm; its shape and size can be achieved by laser cutting, machining, or other methods; and the cross-sectional area of ​​the assembly structure is 0.04 mm. 2 ~400mm 2 Within the size range.

[0096] After the main body of the microstructure is formed by photolithography-electroplating based on the designed microstructure, the method further includes: removing the sacrificial layer of the main body to obtain the final microstructure.

[0097] By employing appropriate sacrificial layer removal methods, the photoresist and seed layer structure in the process are removed, while the electroplated metal structure, assembled ceramic, other metals, polymer and other material structures are retained to obtain the final functional microstructure.

[0098] The corresponding sacrificial layer removal method includes: soaking the microstructure in a photoresist remover solvent to remove the photoresist sacrificial layer; after removing the sacrificial layer, etching with dilute nitric acid to remove the seed layer inside the microstructure and the wafer; and etching with hydrofluoric acid solution to remove the adhesion layer of the microstructure. In addition to the above methods, other sacrificial layer removal methods may also be included, which will not be elaborated upon in this invention.

[0099] It's important to note in this step that specific chemical solvents or physical methods are needed to remove the photoresist and seed layer materials used for temporary support during microstructure fabrication. This step preserves the metal microstructure and the assembled structure, resulting in a functional microstructure composed of heterogeneous structures and different materials such as metals.

[0100] In one specific embodiment, Figure 3 This is a flowchart of a microstructure manufacturing method provided in another embodiment of the present invention; see reference. Figure 3 As shown, the method for manufacturing the microstructure includes:

[0101] Step 101: Use functional software and design the microstructure according to the layered processing rules of the manufacturing process.

[0102] Step 102: Based on the design structure, form a multi-layer sequential processing mask pattern, including multi-layer metal structure electroplating patterns and assembly reserved patterns.

[0103] Step 103: Obtain a wafer substrate, prepare a metal seed layer, and obtain microstructure patterns by photolithography on the wafer surface.

[0104] Step 104: Electroplating metal within the photolithographic pattern to form a metal microstructure, and using a planarization process to control the metal and photoresist to the target thickness to obtain the first layer of the microstructure.

[0105] Step 105: Sequentially use photolithography, electroplating, and planarization processes to obtain other metal layers that do not contain heterostructures.

[0106] Step 106: Photolithography forms a metal structure layer containing pre-reserved assembly positions.

[0107] Step 107: Using a visual recognition, automatic dispensing, and automatic bonding assembly process, the required heterogeneous structural pieces are implanted in the reserved positions.

[0108] Step 108: Obtain a metal structure layer containing assembled heterogeneous structures using electroplating and planarization processes.

[0109] Step 109: Obtain other metal layers that do not contain heterostructures using photolithography, electroplating, and planarization processes. After step 109, when forming other metal layers, steps 106 to 109 may be repeated at least once to complete the assembly of the heterostructure in subsequent layers. The reserved positions for heterostructure assembly can be prepared based on the mask pattern.

[0110] Step 110: After completing the fabrication of all metal layers and the assembly of the structure, remove the photoresist to obtain the final functional heterogeneous integrated microstructure.

[0111] Furthermore, after removing the sacrificial layer of the main portion to obtain the final microstructure, the method further includes: removing the substrate; or dicing the substrate to form an independent device from the entire wafer.

[0112] Furthermore, based on this embodiment, the preparation of the insulating layer and the preparation of the seed layer further include:

[0113] Wafer cleaning: The wafer with the grown oxide insulating layer is cleaned sequentially by 3:1 concentrated sulfuric acid and hydrogen peroxide for 15 minutes, 65℃ hot deionized water, and 20℃ cold deionized water, and then dried in an oven at 110℃-120℃.

[0114] Furthermore, in the thick resist photolithography process, a 110μm-120μm thick layer of photoresist is spin-coated onto the wafer surface. During spin-coating, the uniformity and consistency of the photoresist layer are ensured by adjusting the spin-coating speed and time. Commonly used photoresists include AZnxt125 and N226-30000P.

[0115] In the further electroplating process, direct current or pulse electroplating is used; during the electroplating process, the temperature of the plating solution is controlled within the range of 20-30℃, and any one of the following methods is used: plating solution circulation, cathode oscillation, or rotary electroplating, so that the copper plating thickness is uniform; commonly used electroplating solutions include those based on sulfuric acid and copper sulfate systems.

[0116] In the further assembly process, the assembly pieces are custom-made from the initial design stage. A variety of materials can be selected, including ceramics such as alumina, aluminum nitride, silicon carbide, and zirconium oxide; polymers such as polytetrafluoroethylene, polypropylene, polyimide, and polycarbonate; and other metals such as various steels, ferromagnetic materials, and rare and precious metals. Materials different from the electroplated metal itself are suitable for mechanical support or functional contributions. The thickness is generally in the range of 90-100 μm, and the shape and size can be achieved through laser cutting, machining, etc., with a typical area of ​​0.04 mm. 2 ~400mm 2The size range depends on the specific device structure. For ceramic wafers, a specific adhesive is required, and the dispensing amount is designed based on the properties of the adhesive and the sacrificial photoresist, generally ranging from 0.000125 to 0.2 mL. The heat treatment curing temperature is typically between 50 and 90°C, with a curing time not exceeding 20 minutes. The cured adhesive thickness is between 2 and 10 μm. The assembly structure in this embodiment is an alumina ceramic wafer.

[0117] In the further wafer planarization process, mechanical polishing is first used to grind the copper and photoresist on the wafer surface. When the difference between the thickness of the copper and photoresist on the wafer surface and the target thickness is 3μm-8μm, chemical mechanical polishing is used to further planarize the wafer until the thickness of the copper and photoresist on the wafer surface reaches the target thickness. Mechanical polishing is used for initial planarization of the wafer surface, mainly to grind away 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 thickness of the copper and photoresist and the target thickness decreases to 3μm-8μm, chemical mechanical polishing is switched to the latter.

[0118] Further, the sacrificial layer is removed by immersion in a desizing solvent, commonly NMP organic solvent. During immersion, the solvent temperature should be above 70°C, and the immersion time should be greater than 3 hours. This step effectively dissolves and removes the sacrificial layer. After removing the sacrificial layer, the seed layer inside the micro-coaxial structure and the wafer is removed by etching with 3% (v / v) dilute nitric acid; the adhesion layer is removed by etching with 2% (v / v) hydrofluoric acid solution. The treatment time of the dilute nitric acid should be adjusted according to the actual situation to ensure complete removal of the seed layer. Similarly, the treatment time of the hydrofluoric acid solution should also be adjusted according to actual needs until the adhesion layer is completely removed.

[0119] Example 3:

[0120] This invention provides a method for fabricating a micro-coaxial transmission line, the method comprising:

[0121] S1. Based on the material selection and layer height processing rules of this process, a multi-layered micro-coaxial transmission line is designed. Optionally, a five-layer micro-coaxial transmission line is included, comprising a first to fifth layer of metal structure, and a support structure 3 designed above and below the inner conductor of the micro-coaxial line through an assembly method. Optionally, the support structure 3 is an alumina ceramic structure sheet. The support structure 3 has a height of 100μm, a size of 1mm × 0.5mm, and is placed in the cavity near the port of the coaxial line, forming a clamping relationship with the inner conductor.

[0122] Optionally, during the design process, electromagnetic simulation software such as Ansys HFSS and CST can be used to design the structure and electromagnetic function of the required micro coaxial transmission line. During the design process, the size, position, and number of the three supporting structure pieces that need to be assembled in the designed structure are determined using electromagnetic simulation software.

[0123] S2. Based on the structure designed in S1, a mask pattern is formed. This mask pattern mainly includes the electroplated metal patterns of each layer of the micro-coaxial transmission line, as well as the reserved pattern positions for assembly. The device is fabricated by sequentially combining auxiliary microprocesses such as seed layer preparation and wafer planarization with the main process steps of photolithography, electroplating, and assembly. The specific steps are as follows.

[0124] S21: Obtain wafer 8, and sequentially perform seed layer preparation, thick resist photolithography, electroplating, wafer planarization, and other processes to obtain the first layer of metal microstructure of the micro-coaxial transmission line; Reference Figure 3 As shown.

[0125] The following points need to be explained in this step:

[0126] (1) Wafer 8 can be a silicon wafer or a wafer made of other materials. For example, it can be a compound semiconductor material, such as alumina, silicon carbide (SiC) and gallium arsenide (GaN); it can also be silicon-on-insulator (SOI) material or other new materials. Specifically, if the obtained wafer 8 is a silicon wafer, it generally has a resistivity of 1Ω / cm-10Ω / cm, crystal orientation of 100 or 110, a thickness of 500μm-700μm, and an attached 1μm oxide insulating layer.

[0127] (2) Seed layer preparation is an auxiliary process in this manufacturing method. It is usually done by magnetron sputtering to grow an adhesion layer on the surface of wafer 8 and then sputtering a conductive seed layer on the adhesion layer. The conductive seed layer provides the basis for the subsequent electroplating steps. The adhesion layer is a 20nm-30nm thick titanium adhesion layer and the conductive seed layer is a 300nm-2000nm thick copper conductive seed layer.

[0128] (3) Coat the surface of the conductive seed layer with photoresist 2, and form the bottom surface of the micro-coaxial outer conductor on the substrate according to the first layer of photolithography based on the design structure of the micro-coaxial transmission line; cure, expose and develop the photoresist 2 to obtain the microstructure photolithography pattern.

[0129] (4) Electroplating is the core process step in this manufacturing method: electroplating copper metal on the wafer 8 that forms the microstructure photolithography pattern.

[0130] (5) Wafer planarization is an auxiliary process mainly used to form a consistent plane between the metal structure and the photoresist 2 or the metal structure and the assembly structure. This layer adopts the wafer planarization process to control the thickness of the copper metal and photoresist 2 on the wafer surface to the target thickness, and then obtains the first layer structure of the micro coaxial transmission line. Wafer planarization is usually achieved by wafer mechanical polishing or chemical mechanical polishing technology.

[0131] S22: The second layer of metal microstructure with attached ceramic structure micro-coaxial transmission lines is obtained by sequentially performing thick photolithography, automatic identification dispensing, automatic identification die bonding, electroplating of metallic copper, and wafer planarization; Reference Figures 4-6 As shown.

[0132] The following points need to be explained in this step:

[0133] (1) The thick photolithography, electroplating and wafer planarization processes used in this part are basically the same as those in step S21. Only when the photolithography pattern changes, the corresponding process parameters are adjusted according to the change of pattern area. For example, the change of the size of the electroplating pattern in different layers brings about the change of electroplating current.

[0134] (2) An automatic dispensing machine is used to achieve this. According to the settings, the machine can automatically identify the reserved position of the ceramic structure on the wafer and move the nozzle of the dispensing gun to the center of the reserved position of the ceramic structure. Automatic dispensing is completed by micro-pump control. The dispensing volume ranges from 0.000125 to 0.2 mL. Commonly used chip structure adhesive or similar materials can be used.

[0135] (3) The die bonder using automatic identification technology aligns with the center position of the ceramic structure sheet, picks up the ceramic sheet through the automatic suction nozzle, and then moves and aligns with the center of the reserved position of the ceramic sheet on the wafer. The die bonder controls the vertical movement of the wafer or the suction nozzle so that the ceramic structure sheet is placed in the reserved position of the photolithography master after dispensing and contacts the die bond adhesive. The suction nozzle stops picking up the die, and the ceramic structure sheet is placed in the reserved position. By repeating this step, the assembly and implantation of all ceramic structures on the wafer are completed, and the die bond adhesive is cured in the temperature range of 50-90℃.

[0136] S23: Based on the design structure in S1, repeat and sequentially implement the seed layer deposition, thick resist lithography, copper electroplating, wafer planarization, automatic identification dispensing, and automatic identification die bonding processes in S21 and S22 to complete the third, fourth, and fifth layer structures of the micro-coaxial transmission line in this design; (Reference) Figures 7-9 As shown.

[0137] The following points need to be explained in this step:

[0138] The processes in this step are all repeats of the processes in S21 and S22. The only difference is that when the photolithography pattern changes, the corresponding process parameters are adjusted according to the change in the pattern area. For example, the change in the size of the electroplating pattern in different layers leads to a change in the electroplating current, which is easy to understand in the industry.

[0139] S3: Remove the photoresist sacrificial layer 9 of the microcoaxial transmission line structure, retaining the copper metal structure body and the support structure 3. The support structure 3, implemented and retained through the assembly process, provides good suspension support for the inner conductor of the microcoaxial line, while simultaneously forming an internal air-cavity microcoaxial structure. (Reference) Figure 10 As shown.

[0140] The following points need to be explained in this step:

[0141] This step requires the use of specific chemical solvents or physical methods to remove the photoresist material and seed layer material used in the temporary support structure 3 during the fabrication of the microcoaxial transmission line. This step preserves the metal microstructure and the assembled support structure 3, thereby forming a functional microstructure of the microcoaxial transmission line composed of ceramic and copper.

[0142] refer to Figure 10 , Figure 11 and Figure 12 As shown, the specific structure of a micro-coaxial transmission line includes:

[0143] Transmission line body and multiple supporting structures 3;

[0144] The transmission line body includes an inner conductor and an outer conductor; the outer conductor is disposed outside the inner conductor, and a cavity structure is formed between the inner conductor and the outer conductor;

[0145] Multiple support structures 3 are located within the cavity near the port of the micro coaxial transmission line, with some positioned above the inner conductor and others positioned below it. The multiple support structures 3 form a clamping relationship with the inner conductor to support it.

[0146] In fabricating this microcoaxial transmission line, a first layer structure is first fabricated, followed by the formation of a second layer structure. The first layer structure includes:

[0147] 8 wafers;

[0148] A metallic material layer is disposed on the upper surface of the wafer;

[0149] The first photoresist layer is disposed on the upper surface of the wafer and located on both sides of the metal material layer.

[0150] refer to Figure 10As shown, the outer conductor includes: a first electroplated metal layer 1, and a second layer structure 4, a third layer structure 5, a fourth layer structure 6 and a fifth layer structure 7 formed sequentially on one side of the upper surface of the first electroplated metal layer 1.

[0151] Example 4:

[0152] This embodiment provides a method for fabricating a magnetic core micro inductor, the method comprising:

[0153] (1) Design using HFSS software, such as Figure 22 The micro-inductor structure with a magnetic core shown has a neodymium iron boron alloy permanent magnet in the middle of the copper coil. The upper and lower layers of the permanent magnet are both alumina ceramic sheet structures. The magnetic core and the upper and lower isolation ceramic sheet structures are located in the middle of the entire coil.

[0154] (2) Based on the design structure in (1), form the photolithography pattern of the magnetic core micro inductor.

[0155] (3) Select a 6-inch silicon wafer with a thickness of 500μm and an oxide layer of 1μm on the surface. Clean it with a mixture of concentrated sulfuric acid and hydrogen peroxide, clean it with hot deionized water, clean it with cooled deionized water and dry it. Then, magnetron sputter a 500nm copper film on the surface of the wafer as a seed layer.

[0156] (4) AZnXT125 photoresist is selected. A 115μm thick layer of photoresist is spin-coated onto the seed layer surface in (3), and exposed and developed according to the one-layer structure pattern. Electroplated copper structure, wafer planarization process forms the first layer of metal microstructure for the magnetic micro-inductor, such as... Figure 13 As shown.

[0157] (5) AZnXT125 photoresist is selected, and a 115μm thick layer of photoresist is spin-coated onto the surface of the first layer of the metal microstructure of the magnetic core micro-inductor in (4). Exposure and development are performed according to the two-layer structure layout, reserving the bonding position for the ceramic structure wafer. For example... Figure 14 As shown.

[0158] (6) Using LH-880 epoxy adhesive, an automatic identification dispensing machine is used to dispense 0.01 mL of adhesive onto the pre-reserved ceramic structure sheet position in (5). Then, the automatic identification adhesive machine is used to pick up an alumina ceramic sheet of the designed size and 100 μm thickness, place it at the dispensing position, and cure the adhesive at 80°C for 15 min to stabilize the assembly of the ceramic structure sheet and form 24 layers of adhesive. Figure 15 and Figure 16 As shown.

[0159] (7) The two-layer copper structure of the electroplated magnetic core micro inductor coil has an electroplating thickness of 120 μm. The two-layer microstructure of the magnetic micro inductor is completed using a wafer planarization process. The thickness of this layer is controlled by grinding and polishing to 100 μm, then mechanically polished to 105 μm, and finally chemically mechanically polished to 100 μm. Figure 17 and Figure 18 As shown.

[0160] (8) Repeat steps similar to (5), (6), and (7) to complete the metal (which can be core structure sheet 10) structure processing of the neodymium iron boron core and the third layer of the inductor coil. Figure 19 As shown.

[0161] (9) Repeat similar process steps (5), (6), and (7) to complete the processing of the upper ceramic structure sheet and the fourth metal structure of the inductor coil.

[0162] (10) Repeat steps similar to (4) to complete the fabrication of the entire five-layer structure of the magnetic core micro-inductor. For example... Figure 20 As shown.

[0163] (11) The first sacrificial layer 22 of the photoresist of the magnetic core micro inductor device was removed by soaking in NMP solvent at 70°C for 3.5 hours. Then, the seed layer inside the magnetic core micro inductor structure and the wafer was removed by etching with 3% dilute nitric acid. The adhesion layer was removed by etching with 2% hydrofluoric acid solution.

[0164] (12) Obtain the final magnetic core micro-inductor structure, such as Figure 21 As shown.

[0165] refer to Figure 21 and Figure 22 As shown, specifically, the structure of this magnetic core micro-inductor includes:

[0166] Substrate 21;

[0167] The first electroplated metal layer 23 is disposed on the upper surface of the substrate 21;

[0168] A magnetic core structure 28, wherein ceramic structures 25 are respectively provided on the upper and lower sides of the magnetic core structure;

[0169] The magnetic core structure 28 and the ceramic structure 25 are disposed in the central region of the upper surface of the first electroplated metal layer 23.

[0170] Multiple electroplated metal layers are sequentially stacked on both sides of the upper surface of the first electroplated metal layer 23; the multiple electroplated metal layers surround the magnetic core structure and the ceramic structure.

[0171] Optionally, the multiple electroplated metal layers include a second electroplated metal layer 26, a third electroplated metal layer 27, a fourth electroplated metal layer 29, and a fifth electroplated metal layer 30, which are stacked sequentially. It should be noted that this application describes a manufacturing method for forming functional devices by using photolithography, electroplating, and assembly processes to ultimately achieve the electroplated metal and the assembled heterogeneous structures (ceramics, polymers, other metals). This manufacturing method is not limited to the five-layer structure of the micro-coaxial transmission line and magnetic core micro-inductor mentioned in the embodiments; it can be flexibly adapted according to different functional designs, and this should be understood.

[0172] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this application.

[0173] In the embodiments provided in this disclosure, it should be understood that the disclosed apparatus and methods can also be implemented in other ways. The apparatus embodiments described above are merely illustrative; for example, the flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of apparatus, methods, and computer program products according to various embodiments of this disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram and / or flowchart, and combinations of blocks in block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0174] It should be noted that, in this disclosure, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element limited by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0175] While the embodiments disclosed herein are as described above, the foregoing content is merely for the purpose of facilitating understanding of this disclosure and is not intended to limit this disclosure. Any person skilled in the art to which this disclosure pertains may make any modifications and changes in form and detail of the implementation without departing from the spirit and scope of this disclosure; however, the scope of patent protection of this disclosure shall still be determined by the scope defined in the appended claims.

Claims

1. A method of fabricating microstructures in a litho-electroplating-assembly process, characterized by, The method comprises the following steps: Designing a microstructure according to material selection and layer height processing rules of a process; Forming a main part of the microstructure by a photo-etching and electroplating process based on the designed microstructure; wherein, in the process of forming the main part of the microstructure, a reserved position of an assembled structure is also formed, and the assembled structure is implanted into the reserved position; the assembled structure is a heterogeneous structure; the assembled structure comprises at least one of metal, ceramic and polymer; The implantation of the assembled structure into the reserved position comprises: Using an automatic identification dispensing machine to automatically identify the reserved position of the assembled structure, and moving a glue nozzle of the dispensing gun to the center of the reserved position of the assembled structure to perform dispensing; Using an automatic identification die bonder to align the center position of the assembled structure, and then moving and aligning the center of the reserved position of the assembled structure on a wafer, and controlling the reserved position or the suction nozzle to move in a direction perpendicular to the horizontal direction by the die bonder, so that the assembled structure is placed in the reserved position of the assembled structure after dispensing and contacts the die adhesive, the suction nozzle stops sucking the die, and the assembled structure is implanted into the reserved position of the assembled structure.

2. The method of claim 1, wherein the method is performed by a lithography- electroplating-assembly process. The main part is an electroplated metal.

3. The method of claim 1, wherein the method is characterized by, The forming of the main part of the microstructure by the photo-etching and electroplating process based on the designed microstructure comprises the following steps: Step 011: obtaining a wafer as a substrate, sputtering and growing an adhesion layer on the surface of the wafer based on a design structure, and forming a conductive seed layer on the adhesion layer; Step 012: coating a photoresist on the surface of the conductive seed layer, and performing photo-etching based on a design structure to obtain a photo-etching pattern of the microstructure; Step 013: electroplating a metal material on the wafer on which the photo-etching pattern is formed; Step 014: after the thickness of the metal material and the photoresist on the surface of the wafer is controlled to a target thickness by a planarization process, a first layer structure of the microstructure is obtained; Step 015: repeatedly repeating steps 012-014 on the first layer structure until the main part of the microstructure is obtained.

4. The method of claim 3, wherein the method further comprises: After the forming of the main part of the microstructure by the photo-etching and electroplating process based on the designed microstructure, the following step is further included: removing a sacrificial layer of the main part to obtain a final microstructure.

5. The method of claim 4, wherein the method further comprises: The removing of the sacrificial layer of the main part to obtain the final microstructure comprises the following steps: Soaking the microstructure in a photoresist removing solvent to remove the photoresist sacrificial layer; After the removal of the sacrificial layer, using dilute nitric acid to etch and remove the seed layer inside the microstructure and the wafer; Using a hydrofluoric acid solution to etch and remove the adhesion layer of the microstructure.

6. The method of claim 4, wherein the method further comprises: After the removing of the sacrificial layer of the main part to obtain the final microstructure, the following steps are further included: Removing the substrate; or Carrying out wafer dicing on the substrate to form independent devices from the entire wafer device.

7. The method of claim 1, wherein the method is performed by a litho- electroplating- assembly process. The microstructure comprises a multi-layer structure, and the height of each layer structure is 100 μm or 50 μm.

8. The method of claim 1, wherein the method is performed by a litho- electroplating- assembly process. The forming of the reserved positions of the assembled structures and implanting the assembled structures into the reserved positions include: in the process of forming the main part of the microstructure, the reserved positions of the assembled structures of different levels are formed, and all the assembled structures are implanted into the corresponding reserved positions; the thickness of the assembled structure is 90-100 μm; the cross-sectional area of the assembled structure is 0.04mm 2 -400mm 2 .

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