A down spray wet processing process

Abstract

A down-spraying wet processing technology, steps include: sequentially depositing a growth medium layer and a metal layer on a carrier, then coating photoresist on the metal layer, after exposure and development, preparing for wet etching to remove excess metal; placing the carrier on a carrying table, turning over the carrying table and setting the surface to be processed downward, controlling the temperature of the process cavity and the etching liquid below 60 DEG C; controlling the carrying table to drive the carrier to rotate at a preset speed, controlling the nozzle in the spraying bin to rotate and swing horizontally with preset parameters, spraying etching liquid to the surface of the downwardly arranged mask layer on the carrying table, and forming a liquid track covering the entire mask layer on the surface. The process of the application can forcibly break the liquid boundary layer at low temperature, realize uniform updating and efficient replacement of the liquid, control the line width deviation within ±2μm, and accurately control the side etching amount below 5μm.

Description

Technical Field

[0001] This application belongs to the field of semiconductor and flexible electronics manufacturing technology, and in particular relates to a downspray wet processing technology. Background Technology

[0002] In the manufacturing process of semiconductors and flexible electronic devices, wet processing techniques (such as etching, cleaning, developing, and photoresist stripping) are core steps. Traditional metal etching methods often employ high-temperature environments (typically above 60°C) to accelerate chemical reaction rates and reduce the viscosity and surface tension of the photoresist, aiming to achieve high processing efficiency and uniformity. However, with the development of flexible electronics technology, flexible substrates such as polyimide (PI) are widely used. High-temperature processes (typically above 60°C) can cause thermal stress accumulation, deformation, and even irreversible damage to flexible substrates such as polyimide (PI). They can also cause excessive swelling or peeling of the photoresist, severely affecting pattern accuracy and device yield.

[0003] To address these issues, the industry has attempted wet processing at low temperatures (below 60°C). While low-temperature processes effectively protect flexible substrates and photoresist patterns, they introduce new technical challenges: first, the chemical reaction rate decreases sharply, leading to low processing efficiency; second, the viscosity of the chemical solution increases, resulting in increased surface tension, especially in structures with high aspect ratio micropores or fine lines, making it difficult for the chemical solution to enter or exit, easily creating processing dead zones and residues. Existing low-temperature processes lack effective fluid dynamics design, making it difficult to simultaneously meet the requirements of efficient, uniform, and non-destructive processing. Therefore, a new process capable of achieving high-quality wet processing at low temperatures is urgently needed. Summary of the Invention

[0004] This application aims to solve the technical problems of low reaction rate, incomplete chemical replacement, easy generation of processing dead zones and damage to flexible substrates in existing low-temperature wet processes.

[0005] To solve at least one of the above-mentioned technical problems, the technical solution adopted in this application is: A downspray wet processing technology includes the following steps: A growth medium layer and a metal layer are sequentially deposited on a substrate, and then photoresist is coated on the metal layer. After exposure and development, the substrate is prepared for wet etching to remove excess metal. Place the carrier on the support platform, flip the support platform so that the surface to be processed is facing down, and control the temperature of the process chamber and the etching solution to be below 60°C. The control platform drives the carrier to rotate at a preset speed. Inside the spray chamber, the nozzle is controlled to spray and rotate horizontally at preset parameters, spraying an etching solution onto the mask layer surface facing downwards in the support platform, forming a solution trajectory covering the entire mask layer on its surface.

[0006] Furthermore, the support platform is controlled by a rotary motor and is configured inside the cover via a rotating shaft. The cover is pivotally connected to the end of the robotic arm and can rotate the support platform together. After being rotated, the cover can close the spray chamber to form a sealed spray space. The nozzle is placed inside the spray chamber.

[0007] Furthermore, the support platform is used to fix the carrier thereon; the preset speed of the support platform is 2RPM-300RPM; Preferably, the support platform is provided with a plurality of ejector pins, and a retaining pin is provided on the side of each ejector pin, and the upper end of each retaining pin is provided with a retaining groove for securing the outer diameter of the carrier.

[0008] Furthermore, there are at least two nozzles, which are placed on the pipe. The two ends of the pipe are pivotally connected to parallel swing shafts, which are driven by the same motor to control the horizontal reciprocating swing of the pipe.

[0009] Furthermore, the diameter of the mask layer is smaller than the diameter of the carrier and the nozzle is located directly below the diameter of the mask layer; the length of the pipe is greater than the diameter of the mask layer and crosses the maximum diameter line of the mask layer; the nozzle oscillates at a frequency of 10 times / min to 80 times / min and an amplitude of 20mm to 100mm, and its oscillation angle is 30° to 150°.

[0010] Furthermore, during spray etching, for processes that require chemical potential energy to drive, such as photoresist removal or development, a multi-step chemical displacement method can be adopted. This method is suitable for photoresist removal, development, or metal etching processes. Specifically, it includes a wetting stage, a stripping stage, and a displacement stage performed sequentially. Chemical displacement is achieved by constructing a chemical potential energy gradient to replace thermal energy.

[0011] Furthermore, the wetting stage uses a pressure of 0.05MPa-0.8MPa to spray the chemical solution for 15s-50s; the peeling stage uses a pressure of 0.15MPa-0.8MPa to spray the chemical solution for 20s-80s; the replacement stage uses a pressure of 0.05MPa-0.8MPa to spray the chemical solution for 10s-30s; the total treatment time is less than 150s.

[0012] Furthermore, after the spraying and etching are completed, the surface of the etched mask layer is diluted and rinsed with a cleaning solution. The cleaning solution includes one or more combinations selected from deionized water, isopropanol, N-methylpyrrolidone, acetone, or a surfactant solution; the concentration of the surfactant solution is 0.1%-5%.

[0013] Furthermore, the etching solution used for the spraying etching is selected from one of gold etching solution, copper etching solution, chromium etching solution, or titanium etching solution; wherein, The gold etching solution is prepared based on the total mass ratio, using a solution containing 1%-10% iodine source, 2%-20% co-solvent, and the remainder being deionized water; or, using a solution containing 5%-25% oxidant, 1%-10% complexing agent, 5%-15% acidity regulator, and the remainder being deionized water. The copper etching solution is prepared based on the total mass ratio, using a solution containing 5%-30% ferric chloride, 1%-10% hydrochloric acid, and the remainder being deionized water; or, using a solution containing 5%-20% oxidant, 0.01%-2% corrosion promoter, pH adjuster adjusted to pH 3-6, and the remainder being deionized water. The chromium etching solution is prepared based on the total mass ratio, using a mixture of 5%-25% cerium salt oxidant, 5%-20% inorganic acid, and the remainder being deionized water; or, using a mixture of 1%-10% strong oxidant, 5%-20% strong alkali, 1%-5% complexing agent, and the remainder being deionized water. The titanium etching solution is prepared based on the total mass ratio, using 50%-90% of a 40% ammonium fluoride solution and 10%-50% of a 49% hydrofluoric acid solution; or, using 10%-40% strong acid, 5%-30% oxidant, 1%-5% corrosion inhibitor, with the balance being deionized water.

[0014] Furthermore, after the drug cleaning, a pure water cleaning step is also included, specifically: using deionized water with a resistivity greater than 18 MΩ·cm, spraying and cleaning the mask layer surface under a pressure of 0.1 MPa-0.5 MPa for 20-60 seconds, while controlling the carrier to rotate at a speed of 10 RPM-200 RPM to remove residual drug and cleaning solution.

[0015] The beneficial effects of the downspray wet etching process designed in this application are not simply the sum of various technical features, but rather, through the synergistic effect of multiple physical fields, it resolves the long-standing technical contradiction between low-temperature protection of flexible substrates and efficient and uniform etching. The specific mechanism analysis is as follows: First, it is well known in the art that flexible polyimide substrates experience thermal stress accumulation and irreversible deformation at temperatures above 60°C. Therefore, low-temperature processing (<60°C) is essential for substrate protection. However, low temperatures lead to increased viscosity and surface tension of the etching solution. In traditional spraying or immersion processes, the etching solution struggles to penetrate high aspect ratio microstructures, resulting in a sharp decrease in reaction rate and severe lateral etching. This application utilizes a triple synergistic mechanism of "face down + low-frequency rotation + high-frequency oscillation" to forcibly break the concentration diffusion boundary layer at the solid-liquid interface at low temperatures. The nozzle oscillates at a high frequency of 10-80 times / min, combined with the carrier's low-speed rotation of 2-300 RPM, forming a high-density spiral scouring trajectory on the downward-facing mask surface. This generates localized fluid shear force, allowing fresh etching solution to enter the microstructure through forced convection instead of the inefficient natural diffusion method. Experimental data show that the effective reaction rate generated by this forced convection at low temperatures is equivalent to or even exceeds the reaction rate under traditional high-temperature (>60°C) static conditions, thus overcoming the technical prejudice that "low temperatures inevitably lead to low efficiency."

[0016] Secondly, in traditional processes, reaction byproducts and waste liquids often rely on centrifugal force generated by high-speed rotation (typically >1000 RPM) to be ejected. However, high-speed rotation can cause shear stress damage or even tearing to the flexible substrate. This application utilizes a unique layout with the surface to be treated facing downwards, allowing the waste liquid after the reaction to vertically detach from the micropores and pattern gaps under the dominant force of gravity, without needing to overcome surface tension to overflow upwards or rely on high-speed centrifugal force. Therefore, the carrier rotation speed can be safely controlled within the range of 2-300 RPM, completely avoiding mechanical damage to the flexible substrate caused by high-speed rotation, while also eliminating cleaning dead zones under low temperature and high surface tension conditions.

[0017] Furthermore, this application utilizes a chemical potential energy gradient instead of traditional thermal energy in its multi-step chemical displacement process. Through a three-stage design involving pressure and chemical composition gradients in wetting, peeling, and displacement, it achieves rapid swelling and peeling of thick adhesives at temperatures below 60°C. The total processing time is less than 150 seconds, far superior to the more than 5 minutes required by traditional low-temperature processes, and leaves no visible adhesive residue. This design solves the fundamental problem of insufficient chemical reaction kinetics at low temperatures.

[0018] In summary, this application achieves high precision (linewidth deviation controlled within ±2μm, lateral etching amount ≤5μm), high efficiency (total processing time per wafer <150s), and non-destructive processing of flexible electronic devices at low temperatures through a triple synergy of "ensuring the safety of flexible substrates in low-temperature environment, enhancing chemical thermal energy with mechanical kinetic energy, and reducing interfacial tension barrier with gravity-assisted drainage." This significantly improves the technical level in this field and has outstanding substantive features and significant progress. Attached Figure Description

[0019] Figure 1This is a flowchart of the downspray wet processing technology in this application; Figure 2 This is a three-dimensional view of the carrier structure in this application; Figure 3 This is a diagram of the layer structure of the growth and deposition on the carrier in this application; Figure 4 This is a structural diagram showing the state of the carrier when it is placed on the support platform in this application; Figure 5 This is a schematic diagram of the combination of the downspray wet etching in this application; Figure 6 This is a schematic diagram of the spray chamber in this application; Figure 7 This is a schematic diagram of the sliding fit between the locking post and the support platform in this application.

[0020] In the diagram: 10. Carrier; 11. Isolation layer; 12. Medium layer; 13. Metal layer; 14. Mask layer; 20. Support platform; 21. Ejector pin; 22. Clamping pin; 23. Rotating shaft; 24. Rotary motor; 30. Cover; 40. Spray chamber; 41. Nozzle; 42. Pipe; 43. Swing shaft; 44. Motor; 45. Hose. Detailed Implementation

[0021] The present application will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0022] This embodiment proposes a downspray wet processing technology, such as... Figure 1 As shown, the steps include: S1. A growth medium layer 12 and a metal layer 13 are sequentially deposited on the carrier 10. Photoresist is then coated on the metal layer 13. After exposure and development, a photoresist mask layer is formed. Then, wet etching is prepared to remove excess metal not covered by the mask layer.

[0023] like Figure 2 As shown, silicon wafers with <100>, <111>, or <110> crystal orientations are selected as the rigid carrier 10; alternative materials such as glass, quartz, or sapphire can also be used. Figure 3 As shown, the silicon wafer undergoes a standard RCA cleaning process to remove surface particles and organic matter, and a thin layer of silicon dioxide or silicon nitride is deposited on one side of its surface as an isolation layer 11 to facilitate subsequent carrier removal. Subsequently, in a growth furnace, a dielectric material, such as polyimide (PI) or a similar polymer, is spin-coated or spray-coated onto the silicon wafer surface to form a dielectric layer 12. The spin-coating speed is controlled between 100 rpm and 10000 rpm, and the time is 5 s to 120 s to obtain a uniform dielectric layer 12 with a thickness of 1 μm to 50 μm.

[0024] During actual growth, the diameter of the isolation layer 11 is smaller than the diameter of the silicon wafer, and the center of the isolation layer 11 coincides with the center of the silicon wafer. Preferably, the diameter of the isolation layer 11 is 1 / 3 to 2 / 3 of the diameter of the silicon wafer carrier, leaving a certain edge to facilitate the subsequent removal agent to directly penetrate from the edge of the silicon wafer, accelerating the dissolution or etching of the isolation layer, achieving a gentler and more controllable carrier peeling, and avoiding stress damage caused by large-area uniform removal. At the same time, it can also prevent edge film warping or cracking, and facilitate the silicon wafer edge to be clamped by a robot or chuck. More importantly, when spraying the dielectric layer, there are usually "edge beads" or uneven thickness in the edge area; leaving a blank edge of a certain width can remove these uneven areas, ensuring that the dielectric layer thickness in the central effective area is consistent, thereby improving the accuracy of photolithography alignment and etching. Accordingly, the size of the dielectric layer 12 is adapted to the size of the isolation layer 11.

[0025] After coating, the film is cured by step heating and baking. First, the solvent is evaporated at 50℃-100℃, and then the temperature is raised to 150℃-350℃ to complete imidization. The heating rate is 0.1℃ / min-50℃ / min, and the temperature is held for 1min-120min to prevent the film from cracking and reduce internal stress.

[0026] On the cured dielectric layer 12, an adhesion layer and a conductive layer are sequentially deposited by magnetron sputtering or electron beam evaporation to form a metal layer 13. The adhesion layer, made of Cr, Ti, Ta, W, NiCr, or TiW, has a thickness of 1-100 nm and is used to enhance the bonding force between the metal and the polymer. The conductive layer, made of Au, Cu, Ag, Al, Pt, or Pd, has a thickness of 10-1000 nm.

[0027] After the metal layer 13 is deposited, a photolithography process is used to define the metal pattern: a photoresist is coated, including positive photoresist such as the S1800 series or negative photoresist such as SU-8; then it is exposed and developed, with an exposure wavelength of 365-193nm, and a mask layer 14 is formed after development.

[0028] The entire silicon wafer is then held and placed on the support stage 20 by a robotic arm, ready for wet etching as described in S2-S4 to remove excess metal, and the lateral etching amount is controlled to obtain fine lines with a line width and spacing of 0.5-200μm. After etching, the photoresist is removed, completing the wiring of the metal layer 13.

[0029] S2. Place the carrier 10 on the support platform 20, flip the support platform so that the surface to be processed is facing down, and control the temperature of the process chamber and the etching solution to be below 60°C.

[0030] like Figure 4As shown, the support platform 20 has a circular structure with several ejector pins 21 mounted on it. Preferably, three ejector pins 21 are radially distributed around its center, and the ejector pins 21 are located within its radial plane to uniformly abut against the untreated surface of the silicon wafer. A retaining pin 22 is also disposed beside each ejector pin 21, and the upper end of each retaining pin 22 has a retaining groove for securing the outer diameter of the silicon wafer. When loading the silicon wafer, the wafer is first tilted at a certain angle so that it contacts the retaining groove on one of the retaining pins 22, and then the other side is controlled to be placed horizontally, thus securing the silicon wafer in the retaining groove. This placement method is common and is a standard operation in the art. Of course, the retaining pins 22 and the support platform 20 can also be selected to slide together, such as... Figure 7 As shown, a sliding groove is provided on the support platform 20. The clamping posts 22 are driven by a unified motor to slide along the sliding groove. After the silicon wafer is horizontally placed on the ejector pin 21 by the robot arm, all the clamping posts 22 are controlled to slide from the outside to the inside and the clamping groove clamps the outer edge of the silicon wafer.

[0031] The initial state of the support platform 20 is with its opening facing upwards. It is controlled by the rotary motor 24 and positioned within the cover 30 via the rotating shaft 23. The preset speed of the support platform 20 is 2RPM-300RPM. The cover 30 is generally bowl-shaped, with its outer end pivotally connected to the end of the robotic arm (figure omitted). Controlled by the robotic arm, it can rotate the support platform 20 and the carrier 10 together from horizontal upwards to horizontal downwards. The rotated cover 30 is then controlled to gradually move downwards and close onto the spray chamber 40 to form a sealed spray space; simultaneously, the temperature of the process chamber and the etching solution is controlled to remain below 60°.

[0032] like Figure 5 , Figure 6 As shown, the spray chamber 40 is an upward-opening cavity structure with a drain port at its bottom; nozzles 41 are placed inside it. There are at least two nozzles 41, distributed along a pipe 42. In this embodiment, four nozzles are evenly distributed along the pipe 42. The two middle nozzles 41 are directly connected to the external stock solution via hoses 45 and communicate with the nozzles 41 at both ends via the pipe 42. Simultaneously, both ends of the pipe 42 are pivotally connected to parallel swing shafts 43. The two swing shafts 43 are driven by the same motor 44, enabling horizontal reciprocating swinging of the pipe 42 within the spray chamber 40.

[0033] This downspout design, combined with wafer rotation, ensures that fresh etching solution continuously and evenly covers the entire surface, avoiding inconsistent etching rates caused by solution accumulation or localized concentration differences. This is particularly suitable for fine etching of large-area or high-density patterns (linewidth / spacing 0.5μm-200μm). Furthermore, this embodiment demonstrates that a stable temperature and etching solution concentration can be maintained within a closed spray space, reducing environmental disturbances. Simultaneously, by adjusting the spray pressure and flow rate, the contact time between the etching solution and the metal layer can be controlled, effectively suppressing lateral etching and ensuring the smoothness of the circuit edges (<1μm). Moreover, the closed system prevents splashing and evaporation of strongly acidic or alkaline etching solutions, protecting operators and equipment; and facilitates centralized recycling of waste liquid and acid mist treatment, meeting environmental protection requirements.

[0034] Furthermore, to maximize the spray coverage and trajectory density, the relative dimensions and motion parameters of the nozzles and the mask layer were optimized. The diameter of the mask layer was required to be smaller than the carrier diameter, and the nozzles were positioned directly below the diameter of the mask layer. Simultaneously, the length of the pipe 42, on which the nozzles are mounted, was greater than the diameter of the mask layer 14, and it spanned the maximum diameter line of the mask layer 14. The pipe 42's position directly below the mask layer 14 ensures that, during its reciprocating rotation, the spray width formed by all the nozzles 41 is greater than the diameter of the mask layer 14. This aims to ensure that the width of the spray area formed by the nozzles 41 completely covers the area of ​​the mask layer 14, thereby improving etching uniformity.

[0035] S3. Control the carrier platform 20 to drive the carrier 10 to rotate at a preset speed. In the spray chamber 40, control the nozzle 41 to spray and rotate horizontally at preset parameters to spray an etching solution onto the surface of the mask layer 14 set downward in the carrier platform 20, forming a liquid trajectory covering the entire mask layer 14 on its surface.

[0036] By combining mechanical motion with fluid control, efficient and uniform coverage of the etching solution on the surface of the wafer mask layer can be achieved at low temperatures. Specifically, the stage 20 is controlled to rotate the carrier (wafer) 10 at a preset speed, while the nozzles in the sealed spray chamber spray the etching solution while simultaneously oscillating horizontally. This combination of rotation and oscillation creates a continuous and interwoven spiral trajectory of the etching solution on the downward-facing mask layer 14. Even if the viscosity and surface tension of the etching solution increase at low temperatures, this cleaning process can break the diffusion boundary layer at the solid-liquid interface, promoting continuous renewal of the etching solution and preventing localized depletion or the creation of cleaning dead zones, thereby ensuring the uniformity of etching across the entire surface.

[0037] like Figure 6As shown, during the oscillation, nozzle 41 oscillates at a frequency of 10-80 times / min and an amplitude of 20-100mm, with an oscillation angle between 30° and 150°. Because the wafer rotates, nozzle 41 oscillates simultaneously, causing the liquid to trace a spiral-like path on the wafer surface. As nozzle 41 oscillates back and forth, this spiral repeatedly sweeps across different areas of the wafer, and after multiple rotations, the spirals at different times intersect and overlap, forming an interwoven mesh-like coverage. Furthermore, the simultaneous oscillation of four nozzles 41 generates multiple interwoven spirals, further densifying the coverage. These parameters, combined with the low-speed rotation (2RPM-300RPM) of carrier 10, create a spiral-interwoven liquid trajectory resulting from the superposition of low-frequency rotation and high-frequency oscillation, ensuring that the liquid spray path sweeps across the surface of mask layer 14 and that the liquid completely covers mask layer 14. It significantly increases the contact probability between the solution and the mask layer surface, which is especially beneficial for solution replacement in the interior and edge areas of micro-patterns, ultimately laying the flow field foundation for subsequent high-precision etching.

[0038] Furthermore, in addition to the coordination of mechanical motion, this process also introduces a multi-step chemical displacement method during the spraying and etching process, specifically for scenarios requiring chemical potential energy, such as photoresist removal or development. This includes sequential wetting, stripping, and displacement stages. The core principle is to utilize the gradient changes in the chemical potential energy of the chemical solution at different stages to replace the heat energy provided by traditional high temperatures.

[0039] Specifically, in the wetting stage, the chemical solution is sprayed at a pressure of 0.05MPa-0.8MPa for 15-50 seconds to fully wet the photoresist surface. In the stripping stage, the pressure is increased and maintained within the range of 0.15MPa-0.8MPa for 20-80 seconds, utilizing the chemical potential energy gradient to induce the photoresist to swell, peel off, and detach from the metal surface. Finally, in the replacement stage, a pressure of 0.05MPa-0.8MPa is sprayed for 10-30 seconds to displace and remove the reaction products and residual chemical solution. The total processing time is controlled to be less than 150 seconds. This operation can be performed at low temperatures below 60°C by constructing a chemical potential energy gradient to replace thermal input. It relies entirely on the chemical potential energy gradient, rather than thermal energy, to cause the photoresist to swell, peel off, and be removed, thus completely avoiding thermal damage to the flexible polyimide (PI) substrate or metal layer caused by high temperatures. At the same time, it significantly shortens the photoresist removal time (traditional processes often require more than 5 minutes) and leaves no visible photoresist residue.

[0040] Finally, regarding the selection of etching solutions, this process offers a variety of suitable formulations for different metal materials to ensure accurate etching results even at low temperatures. The etching solutions used are selected from one of the following: gold etching solution, copper etching solution, chromium etching solution, or titanium etching solution, specifically including: (a) Gold etching solution, which has two formulations: Formula 1: An iodine-based system formulated based on the total mass ratio of the etching solution, with the following components and mass percentage ranges: iodine source (iodine element) 1%-10%, co-solvent (potassium iodide) 2%-20%, and the balance being deionized water.

[0041] Formula 2: A thiourea / acidic system prepared based on the total mass ratio of the etching solution. Its components and mass percentage range are as follows: oxidant (hydrogen peroxide or nitrate) 5%-25%, complexing agent (thiourea) 1%-10%, acidity regulator (sulfuric acid) 5%-15%, and the balance is deionized water.

[0042] (b) Copper etching solution, which has two formulations: Formula 1: A ferric chloride system prepared based on the total mass ratio of the etching solution, with the following components and mass percentage range: ferric chloride (FeCl3) 5%-30%, hydrochloric acid (HCl) 1%-10%, and the balance being deionized water.

[0043] Formula 2: A persulfate system based on the total mass ratio of the etching solution. Its components and mass percentage range are as follows: oxidant (sodium persulfate or ammonium persulfate) 5%-20%, corrosion promoter (benzotriazole BTA) 0.01%-2%, pH adjuster (ammonia or sulfuric acid) to adjust the pH value to 3-6, and the balance is persulfate in deionized water.

[0044] (c) Chromium etching solution, which has two formulations: Formula 1: A cerium ammonium nitrate system prepared based on the total mass ratio of the etching solution. Its components and mass percentage range are: cerium salt oxidant (cerium ammonium nitrate) 5%-25%, inorganic acid (nitric acid) 5%-20%, and the balance is deionized water.

[0045] Formula 2: Based on the total mass ratio of the etching solution, the permanganate system has the following components and mass percentage range: strong oxidant (potassium permanganate) 1%-10%, strong alkali (sodium hydroxide) 5%-20%, complexing agent (sodium citrate) 1%-5%, and the balance is deionized water.

[0046] (d) Titanium etching solution, which has two formulations: Formula 1: An ammonium fluoride / hydrofluoric acid system prepared based on the total mass ratio of the etching solution, with the following composition and mass percentage range: 50%-90% ammonium fluoride solution with a concentration of 40% and 10%-50% hydrofluoric acid solution with a concentration of 49%.

[0047] Formula 2: A sulfuric acid / hydrogen peroxide system prepared based on the total mass ratio of the etching solution. Its components and mass percentage range are: strong acid (concentrated sulfuric acid) 10%-40%, oxidant (hydrogen peroxide) 5%-30%, corrosion inhibitor (phosphoric acid) 1%-5%, and the balance is deionized water.

[0048] The aforementioned formulation maintains an appropriate etching rate even at low temperatures. Combined with the aforementioned rotational oscillation and multi-step replacement process, it enables high-precision pattern transfer with a lateral etching depth of ≤5μm and a linewidth deviation of ≤±2μm, while ensuring no thermal damage to the flexible substrate and the integrity of the photoresist pattern. This method overcomes the problem of insufficient reaction kinetics at low temperatures, combining the precision of chemical formulation with physical flow field disturbances, providing a reliable wet processing solution for high-yield manufacturing of flexible electronic devices.

[0049] S4. After the spraying and etching are completed, the surface of the etched mask layer 14 is diluted and rinsed with a cleaning solution.

[0050] After the etching of mask layer 14 is completed, the surface needs to be cleaned to promptly stop the etching reaction and remove residual reagents and reaction products. Specifically, this involves diluting and rinsing the mask layer surface with a cleaning solution selected from one or more combinations of deionized water, isopropanol, N-methylpyrrolidone, acetone, or a surfactant solution, wherein the concentration of the surfactant solution is controlled between 0.1% and 5%. By selecting appropriate cleaning solution components, etching residues of different properties, such as organic photoresist fragments and metal ion complexes, can be effectively dissolved or emulsified, preventing the residues from being re-adsorbed or precipitated during subsequent drying, thereby ensuring the cleanliness of the mask pattern edges.

[0051] To further improve cleaning efficiency and avoid residue redeposition caused by sudden changes in cleaning solution concentration, a gradient dilution rinsing method is adopted in this step. Specifically, a higher concentration of the first cleaning solution is sprayed for 10-20 seconds at a pressure of 0.2MPa-0.4MPa to quickly peel off and remove most of the residual solution. Immediately afterwards, a second cleaning solution with a lower concentration than the first cleaning solution is used and sprayed for another 10-15 seconds at a lower pressure of 0.1MPa-0.3MPa. This gradient rinsing method, from concentrated to diluted, creates a gradually changing chemical environment on the surface of the mask layer 14, allowing the residue to be gradually diluted and removed, rather than flocculating or re-attaching due to excessive instantaneous concentration differences. This ensures thorough cleaning while avoiding excessive impact or corrosion of fine microstructures (especially in high aspect ratio holes or between fine lines) by high-concentration cleaning solutions. At the same time, the pressure segmentation control achieves an optimized match between mechanical scouring force and chemical dissolution.

[0052] S5. After cleaning with the chemical solution, a rinsing process using pure water is also included.

[0053] After the gradient dilution rinsing described above, trace amounts of cleaning solution components or trace ions may still remain on the surface of the mask layer. Therefore, a final rinse with ultrapure water is required. Specifically, deionized water (i.e., ultrapure water) with a resistivity greater than 18 MΩ·cm is used to spray and clean the mask layer surface under a pressure of 0.1 MPa-0.5 MPa for 20-60 seconds. Simultaneously, the carrier (wafer) is continuously rotated at a speed of 10-200 RPM, utilizing centrifugal force to assist in removing the residual liquid film on the surface, thus removing residual chemicals and cleaning solution. The centrifugal force from the rotation helps to dislodge water droplets adhering to the surface, while the high solubility of ultrapure water effectively removes any residual organic or inorganic impurities. Thorough removal of the cleaning solution introduced in the previous steps and unreacted etching solution ensures that the mask layer surface achieves extremely high cleanliness (e.g., surface residual ion concentration below 1 ppb), providing a contamination-free foundation for subsequent drying or the next process (such as resist removal or inspection). At the same time, appropriate rotation speed combined with spray pressure can avoid graphic defects (such as watermarks and crystallization points) caused by water residue during the drying process, thereby ensuring that the final line width deviation is controlled within ±2μm and the lateral erosion amount is ≤5μm, achieving a high-precision machining target.

[0054] This application is not a simple physical superposition of low temperature and downward spraying, but rather a collaborative mechanism to solve the contradiction between "thermal damage-reaction rate-pattern accuracy" in wet processing of flexible substrates through the coordinated motion of dual-axis motion of low-frequency rotation and high-frequency oscillation and the flow field design of gravity-assisted drainage. First, addressing the issues of thermal stress deformation and photoresist swelling in flexible polyimide (PI) substrates caused by traditional high-temperature processes (>60℃), this application strictly controls the temperature of the process chamber and reagent below 60℃, eliminating thermal damage at its source. However, low temperatures lead to increased reagent viscosity and surface tension, causing a sharp decrease in reaction rate and severe lateral etching under traditional processes. To address this, this application utilizes the superposition of high-frequency nozzle oscillation (10-80 times / min) and low-speed carrier rotation (2RPM-300RPM) to form a high-density spiral erosion trajectory on the downward-facing mask surface. This specific flow field generates local shear force, forcibly breaking the stable diffusion boundary layer at the solid-liquid interface under low-temperature, high-viscosity conditions. This forces fresh reagent to enter the microstructure via convection rather than inefficient diffusion, achieving efficient chemical potential energy-driven displacement. Experiments demonstrate that this forced convection efficiency at low temperatures is equivalent to or even exceeds the reaction rate under high-temperature static conditions.

[0055] Furthermore, this application utilizes a layout with the surface to be processed facing downwards, converting gravity into drainage power. The waste liquid after the reaction vertically detaches from the micropores and pattern gaps under gravity, eliminating the need to overcome surface tension to overflow upwards or rely on high-speed centrifugal force for horizontal ejection, thus completely eliminating cleaning dead zones under low-temperature, high-surface-tension conditions. This allows the carrier rotation speed to be reduced to a safe threshold of 2-300 RPM, far lower than the risk of shearing and tearing of flexible substrates caused by traditional high-speed rotation (>1000 RPM). In summary, this application overcomes long-standing technical biases in the field through a triple synergistic approach: ensuring substrate safety in a low-temperature environment, compensating for chemical heat energy with mechanical kinetic energy, and removing the tension barrier through gravity drainage. This enables high-precision, high-efficiency wet processing of flexible electronic devices at low temperatures.

[0056] The bottom-spray wet processing technology designed in this application controls the process environment within a low temperature range below 60°C, fundamentally avoiding thermal damage to the flexible substrate and photoresist swelling caused by high-temperature processing, thus providing a damage-free process foundation for high-precision processing. Furthermore, through the synergistic effect of carrier rotation and nozzle oscillation, the chemical boundary layer is forcibly broken at low temperatures, achieving uniform renewal and efficient replacement of the chemical solution. This controls linewidth deviation within ±2μm and lateral etching depth precisely below 5μm. Simultaneously, a multi-step gradient chemical replacement method is employed, using chemical potential energy instead of thermal energy to drive the process. Thick resist removal and deep cleaning of the microstructure can be completed within 150s, completely solving the technical problems of high surface tension and easy formation of processing dead zones at low temperatures, significantly improving the pattern accuracy and yield of flexible precision devices.

[0057] The embodiments of this application have been described in detail above. These descriptions are merely preferred embodiments and should not be construed as limiting the scope of this application. All equivalent variations and modifications made within the scope of this application should still fall within the patent coverage of this application.

Claims

1. A downspray wet processing technology, characterized in that the steps include... include: A growth medium layer and a metal layer are sequentially deposited on a substrate, and then photoresist is coated on the metal layer. After exposure and development, the substrate is prepared for wet etching to remove excess metal. Place the carrier on the support platform, flip the support platform so that the surface to be processed is facing down, and control the temperature of the process chamber and the etching solution to be below 60°C. The control platform drives the carrier to rotate at a preset speed. Inside the spray chamber, the nozzle is controlled to spray and rotate horizontally at preset parameters, spraying an etching solution onto the mask layer surface facing downwards in the support platform, forming a solution trajectory covering the entire mask layer on its surface.

2. The downspray wet processing technology according to claim 1, characterized in that, The support platform is controlled by a rotary motor and is configured inside the cover via a rotating shaft. The cover is pivotally connected to the end of the robotic arm and can rotate the support platform together. After being rotated, the cover can close the spray chamber to form a sealed spray space. The nozzle is placed inside the spray chamber.

3. A downspray wet processing technology according to claim 1 or 2, characterized in that, The support platform is used to fix the carrier thereon; the preset speed of the support platform is 2RPM-300RPM; Preferably, the support platform is provided with a plurality of ejector pins, and a retaining pin is provided on the side of each ejector pin, and the upper end of each retaining pin is provided with a retaining groove for securing the outer diameter of the carrier.

4. The downspray wet processing technology according to claim 3, characterized in that, There are at least two nozzles, which are placed on the pipe. The two ends of the pipe are pivotally connected to parallel swing shafts, which are driven by the same motor to control the horizontal reciprocating swing of the pipe.

5. The downspray wet processing technology according to claim 4, characterized in that, The diameter of the mask layer is smaller than the diameter of the carrier and the nozzle is located directly below the diameter of the mask layer; the length of the pipe is greater than the diameter of the mask layer and crosses the maximum diameter line of the mask layer; the nozzle oscillates at a frequency of 10 times / min-80 times / min and an amplitude of 20mm-100mm, and its oscillation angle is 30°-150°.

6. A downspray wet processing method according to any one of claims 1-2 and 4-5, characterized in that, Multi-step chemical replacement is used in spray etching, which is suitable for photoresist removal, development or metal etching processes. Specifically, it includes a wetting stage, a stripping stage and a replacement stage in sequence. Chemical replacement is achieved by constructing a chemical potential energy gradient to replace thermal energy.

7. The downspray wet processing technology according to claim 6, characterized in that, The wetting stage uses a pressure of 0.05MPa-0.8MPa to spray the chemical solution for 15s-50s; the peeling stage uses a pressure of 0.15MPa-0.8MPa to spray the chemical solution for 20s-80s; the replacement stage uses a pressure of 0.05MPa-0.8MPa to spray the chemical solution for 10s-30s; the total treatment time is less than 150s.

8. The downspray wet processing technology according to claim 7, characterized in that, The etching solution used for spraying is selected from one of the following: gold etching solution, copper etching solution, chromium etching solution, or titanium etching solution; wherein... The gold etching solution is prepared based on the total mass ratio, using a solution containing 1%-10% iodine source, 2%-20% co-solvent, and the remainder being deionized water; or, using a solution containing 5%-25% oxidant, 1%-10% complexing agent, 5%-15% acidity regulator, and the remainder being deionized water. The copper etching solution is prepared based on the total mass ratio, using a solution containing 5%-30% ferric chloride, 1%-10% hydrochloric acid, and the remainder being deionized water; or, using a solution containing 5%-20% oxidant, 0.01%-2% corrosion promoter, pH adjuster adjusted to pH 3-6, and the remainder being deionized water. The chromium etching solution is prepared based on the total mass ratio, using a mixture of 5%-25% cerium salt oxidant, 5%-20% inorganic acid, and the remainder being deionized water; or, using a mixture of 1%-10% strong oxidant, 5%-20% strong alkali, 1%-5% complexing agent, and the remainder being deionized water. The titanium etching solution is prepared based on the total mass ratio, using 50%-90% of a 40% ammonium fluoride solution and 10%-50% of a 49% hydrofluoric acid solution; or, using 10%-40% strong acid, 5%-30% oxidant, 1%-5% corrosion inhibitor, with the balance being deionized water.

9. A downspray wet processing method according to any one of claims 1-2, 4-5, and 7-8, characterized in that, After the spraying and etching are completed, the surface of the etched mask layer is diluted and rinsed with a cleaning solution. The cleaning solution is selected from one or more combinations of deionized water, isopropanol, acetone or surfactant solution; the concentration of the surfactant solution is 0.1%-5%.

10. The downspray wet processing technology according to claim 9, characterized in that, After the chemical cleaning, a pure water cleaning step is also included, specifically: using deionized water with a resistivity greater than 18 MΩ·cm, spraying and cleaning the surface of the mask layer under a pressure of 0.1 MPa-0.5 MPa for 20-60 seconds, while controlling the carrier to rotate at a speed of 10 RPM-200 RPM to remove residual chemical and cleaning solutions.

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