Method for removing photoresist and semiconductor structure

Abstract

The application relates to a photoresist removal method and a semiconductor structure, and relates to the technical field of semiconductor manufacturing. The method comprises the following steps: providing a target etching solution comprising a nucleophile and a peroxide; immersing a semiconductor structure to be washed, which has a carbon-containing photoresist on the surface, in the target etching solution which is preheated to a preset temperature until the cleaning time reaches a preset length; the nucleophile provides at least an electron-rich nucleophilic center for nucleophilic bond breaking of a reticular high-molecular in the carbon-containing photoresist into soluble small molecules; the peroxide provides at least an oxidatively active chemical bond for oxidizing and destructing a carbonized layer in the carbon-containing photoresist to destroy the compactness of the carbonized layer; the carbonized layer on the surface of the carbon-containing photoresist is used for in-situ catalysis and enhancement of the efficiency of the nucleophilic bond breaking and the ability of the oxidizing and destructing through electron conduction and interfacial activation; after the semiconductor structure is etched by taking out the target etching solution, the semiconductor structure is sequentially subjected to rinsing, washing, and blowing dry by inert gas to remove residual target etching solution, and the target semiconductor structure is obtained.

Description

Technical Field

[0001] This application relates to the field of semiconductor manufacturing technology, and in particular to a method for removing photoresist and a semiconductor structure. Background Technology

[0002] Photoresist is a photosensitive organic polymer film used for pattern transfer in semiconductor manufacturing. After key processes such as photolithography, etching, and ion implantation, this temporary film must be completely removed; otherwise, it can easily leave impurities, contaminate subsequent processes, and ultimately lead to device failure.

[0003] However, the wet degumming process in related technologies has a poor degumming effect. Summary of the Invention

[0004] Therefore, it is necessary to provide a method for removing photoresist with better resist removal effect and a semiconductor structure.

[0005] In a first aspect, this application provides a method for removing photoresist, comprising:

[0006] A non-aqueous target etching solution is provided, the target etching solution comprising a nucleophile and a peroxide; the nucleophile includes organic ethers.

[0007] The semiconductor structure to be cleaned, with carbon-containing photoresist on its surface, is immersed in a target etching solution preheated to a preset temperature until the cleaning time reaches a preset duration. The nucleophile provides at least electron-rich nucleophilic centers to nucleophilically break the bonds of the network polymer in the carbon-containing photoresist into soluble small molecules. The peroxide provides at least oxidatively active chemical bonds to oxidize and deconstruct the carbonized layer in the carbon-containing photoresist, thereby disrupting its compactness. The carbonized layer on the surface of the carbon-containing photoresist is used to catalyze and enhance the efficiency of nucleophilic bond breaking and the ability of oxidative deconstruction through electron conduction and interface activation.

[0008] The semiconductor structure removed from the target etching solution is rinsed and washed sequentially, and then dried with inert gas to remove the residual target etching solution.

[0009] In some embodiments, the target etching solution includes a main solvent for dissolving nucleophiles and peroxides; the main solvent is used at least to swell and permeate the carbon-containing photoresist.

[0010] In some embodiments, the main solvent includes γ-butyrolactone, γ-valerolactone, N-methylpyrrolidone, and propylene carbonate.

[0011] In some embodiments, the target etching solution further includes a penetration enhancer, which is used to enhance the penetration of the target etching solution into the gaps of the carbonized layer.

[0012] In some embodiments, the penetration enhancer includes diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, or ethylene glycol dimethyl ether.

[0013] In some embodiments, the target etching solution further includes an organic adsorption type corrosion inhibitor, which is used to form a dense, insoluble polymer protective film with the copper or copper alloy surface in the semiconductor structure to be cleaned through chemical adsorption, thereby blocking the target etching solution.

[0014] In some embodiments, the organic adsorbent corrosion inhibitor includes benzotriazole, methylbenzotriazole, 2-mercaptobenzothiazole, or combinations thereof.

[0015] In some embodiments, the nucleophile further includes an organic alcohol amine reagent, wherein the organic alcohol amine reagent includes monoethanolamine, diethanolamine, triethanolamine, N,N-dimethylethanolamine, N-methylethanolamine, or combinations thereof.

[0016] In some embodiments, the organic ether reagent includes ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol dimethyl ether, or combinations thereof.

[0017] In some embodiments, the peroxide includes anhydrous tert-butyl hydroperoxide or cumene hydroperoxide.

[0018] In some embodiments, the preset temperature is 60°C to 90°C.

[0019] In some embodiments, the preset duration is 8 min to 20 min.

[0020] In some embodiments, isopropanol is used to rinse the semiconductor structure removed from the target etching solution to remove residual target etching solution; wherein the rinsing temperature is 40°C to 60°C and the rinsing time is 5 min to 10 min.

[0021] In some embodiments, the semiconductor structure is rinsed with deionized water.

[0022] In some embodiments, the target semiconductor structure is dried with nitrogen gas after the residual target etching solution has been removed.

[0023] In some embodiments, megasonic-assisted wet etching is performed during the immersion of the semiconductor structure to be cleaned in the target etching solution.

[0024] In some embodiments, the semiconductor structure to be cleaned includes a patterned gate structure located on a substrate.

[0025] Secondly, this application provides a semiconductor structure in which the photoresist is removed using the photoresist removal method described in any of the above embodiments.

[0026] The above-mentioned photoresist removal method and semiconductor structure can produce at least the following unexpected technical effects:

[0027] First, a target etching solution comprising nucleophiles and peroxides is provided. The semiconductor structure to be cleaned is then immersed in the target etching solution preheated to a preset temperature, allowing the carbon-containing photoresist on the surface of the semiconductor structure to react with the target etching solution for a preset time. Since the peroxides in the target etching solution can provide oxidizing active chemical bonds, they can destroy the dense graphite-like crystal structure of the carbonized layer on the surface of the carbon-containing photoresist through oxidation, creating numerous micropores and cracks. Furthermore, since the nucleophiles can provide electron-rich nucleophilic centers, they can break the three-dimensional network of polymer chains within the photoresist into small molecule fragments soluble in the etching solution. Additionally, the carbonized layer on the surface of the carbon-containing photoresist contains numerous defect sites and unsaturated bonds, which can adsorb and enrich nucleophiles and peroxide molecules in the target etching solution, increasing the local concentration at the reaction interface, thereby improving the efficiency of nucleophilic bond breaking and the ability of oxidative deconstruction. Therefore, after cleaning the semiconductor structure with the target etching solution for the preset time, the carbon-containing photoresist on the surface of the semiconductor structure can be effectively removed. Then, the etched semiconductor structure is rinsed and washed in sequence to remove the residual target etching solution on the semiconductor structure, and the target semiconductor structure is obtained. After that, the target semiconductor structure is dried with inert gas to obtain a clean target semiconductor structure without residue. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a flowchart of a photoresist removal method provided in one embodiment;

[0030] Figure 2 This is a flowchart of a photoresist removal method provided in another embodiment. Detailed Implementation

[0031] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0032] In related technologies, dry or wet photoresist removal processes are commonly used. Dry photoresist removal utilizes high-energy plasma generated by ionizing gases such as oxygen in a vacuum. This plasma, through physical bombardment and chemical reactions, oxidizes and decomposes the photoresist into gaseous products (such as CO2 and H2O), which are then discharged. Wet photoresist removal involves immersing the wafer in a specific chemical reagent, dissolving the photoresist through a chemical reaction. This process can be accelerated by combining ultrasonic / megasonic mechanical vibrations. Compared to dry photoresist removal, wet photoresist removal offers advantages such as higher removal efficiency, better selectivity, and no damage to the underlying silicon. Therefore, it is more widely used in photoresist removal. However, wet photoresist removal also has the following drawbacks:

[0033] First, photoresist is an organic polymer. During the ion implantation stage of semiconductor fabrication, when the implantation dose is high, the ion mass is heavy, and the energy is high, the high-energy ions violently bombard the photoresist molecules, breaking the long-chain structure of the organic polymer and inducing intense intermolecular cross-linking, forming a three-dimensional network structure. Ultimately, this leads to carbonization and hardening of the photoresist surface, forming a dense, hard, and chemically inert carbonized layer. Wet photoresist removal in related technologies relies on chemical reagents to dissolve soluble organic polymers. However, the carbonized layer is essentially a graphite-like structure, almost insoluble in any strong acid, strong alkali, or organic solvent. Therefore, the wet photoresist removal process becomes unsuitable in this situation.

[0034] Secondly, to improve the rate and effect of resist removal, wet resist removal processes typically use strong oxidizing acids (such as concentrated sulfuric acid, concentrated nitric acid, or hydrofluoric acid) and are carried out at high temperatures. This can slightly etch other materials on the wafer. For example, the silicon substrate can be slowly corroded by hydrofluoric acid or hot concentrated sulfuric acid, and the metal layers (metal gates or contact layers such as aluminum, copper, titanium, and titanium nitride) can be corroded by strong acids. This may result in narrower linewidths or deeper trenches, causing transistor threshold voltage drift; corrosion of metal contact layers leads to a decrease in current transmission efficiency; thinning of the dielectric layer or the appearance of pinholes leads to a decrease in device insulation performance; corrosion defects on the material surface can become carrier traps, accelerating device aging and other problems, affecting the electrical performance of the device.

[0035] Third, wet degumming processes consume a large amount of chemical reagents, and in order to ensure the degumming effect, the reagents need to be replaced frequently, resulting in high consumable costs; concentrated sulfuric acid and concentrated nitric acid are highly corrosive, and strong oxidizing reagents at high temperatures are prone to splashing, posing a high safety hazard; at the same time, wet degumming processes in related technologies also generate a large amount of acidic waste liquid containing heavy metal ions and organic pollutants, resulting in high treatment costs.

[0036] To address the aforementioned technical problems, please refer to some exemplary embodiments. Figure 1 This application provides a method for removing photoresist, the method comprising steps S101 to S103.

[0037] S101: Provides target etching solution for non-aqueous systems.

[0038] The target etching solution includes nucleophiles and peroxides.

[0039] Nucleophilic reagents (Nu, also known as nucleophilic groups) are a class of nucleophilic chemical reagents, belonging to Lewis bases, capable of donating electron pairs to attack electron-deficient centers. In the embodiments of this application, nucleophilic reagents may include organic alcohol amines and / or organic ethers. The organic alcohol amines include at least monoethanolamine, diethanolamine, triethanolamine, N,N-dimethylethanolamine, N-methylethanolamine, or combinations thereof. The organic ethers include at least ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol dimethyl ether, or combinations thereof.

[0040] Peroxides are compounds containing a peroxide group (-OO-), possessing strong oxidizing properties, and can be divided into inorganic and organic categories. In the embodiments of this application, the peroxides include at least anhydrous tert-butyl hydroperoxide or cumene hydroperoxide.

[0041] Monoethanolamine (MEA), with the chemical formula C2H7NO, is a colorless, transparent, viscous liquid that turns into a white crystalline solid when cold. It has a faint ammonia odor, is strongly alkaline, hygroscopic, readily soluble in water and alcohols, and slightly soluble in benzene and ether.

[0042] Diethanolamine (DEA), also known as 2,2'-dihydroxydiethylamine, is an organic compound with the chemical formula C4H. 11 NO2.

[0043] Triethanolamine (TEA) is an organic compound with the chemical formula C6H. 15 NO3, similar to other amine compounds, has a weak basicity due to the lone pair of electrons on the nitrogen atom, and can react with inorganic or organic acids to form salts.

[0044] N,N-Dimethylethanolamine (DEMA) is an organic compound with the chemical formula C4H. 11 NO is mainly used as a resin raw material, and also as a raw material for pharmaceuticals, dyes and paint solvents.

[0045] N-Methylethanolamine (MMEA) is an organic compound with the chemical formula C3H9NO.

[0046] Ethylene glycol monomethyl ether (DME) is an organic compound with the chemical formula C3H8O2. It is a colorless and transparent liquid that is miscible with water and alcohols, ketones, and hydrocarbons.

[0047] Diethylene glycol monomethyl ether (DGDE), also known as diethylene glycol methyl ether, has the chemical formula C5H. 12 O3.

[0048] Triethylene glycol dimethyl ether, also known as triethylene glycol dimethyl ether, has the chemical formula C8H. 18 O4 is an ethylene glycol ether organic compound that is a colorless liquid at room temperature, soluble in water, and has high thermal stability and strong solvation ability.

[0049] Anhydrous tert-butyl hydroperoxide (TBHP) is an organic peroxide with the chemical formula C4H. 10 O2 is a colorless liquid with a volatile aroma at room temperature. Tert-butanol peroxide is a strong oxidizing agent with a strong oxidizing ability towards organic matter. It can react with many substances, such as alcohols, ethers, aldehydes, and ketones. In the reaction, it breaks off an oxygen molecule, forming a free radical, which leads to the oxidation of the substance.

[0050] Cumene hydroperoxide (CHP), chemical formula C9H 12 O2 is a colorless to pale yellow liquid, readily soluble in ethanol, acetone, esters, hydrocarbons and chlorinated hydrocarbons, and slightly soluble in water.

[0051] S102: Immerse the semiconductor structure to be cleaned, which has carbon photoresist on its surface, in a target etching solution preheated to a preset temperature until the cleaning time reaches the preset duration.

[0052] Among them, the nucleophile provides at least an electron-rich nucleophilic center to nucleophilically break the bonds of the network polymer in the carbon-containing photoresist into soluble small molecules; the peroxide provides at least an oxidatively active chemical bond to oxidize and deconstruct the carbonized layer in the carbon-containing photoresist to destroy its compactness; the carbonized layer on the surface of the carbon-containing photoresist is used to catalyze in situ and enhance the efficiency of nucleophilic bond breaking and the ability of oxidative deconstruction through electron conduction and interface activation.

[0053] In the embodiments of this application, when the semiconductor structure to be cleaned with carbon photoresist on its surface is immersed in the target etching solution at a preset temperature, the target etching solution first penetrates into the tiny gaps naturally present in the carbonized layer through capillary action.

[0054] Because the carbonized layer has graphite-like semiconductor conductivity, it can act as a bridge for electron transfer. Therefore, the carbonized layer can catalyze the decomposition of peroxides to generate highly oxidizing active species. In turn, the highly oxidizing active species oxidize and open the fused rings and conjugated structures of the carbonized layer, destroying the density of the carbon layer and causing it to become unstable and fall off, generating more new gaps and channels, allowing more target etching solution to penetrate into the interior of the carbon-containing photoresist.

[0055] Simultaneously, catalyzed by the carbonized layer, the nucleophilic centers can efficiently attack the cross-linked structures of the photoresist, such as COC, ester bonds, and ether bonds, causing the three-dimensional network polymer to depolymerize into soluble small molecules. These small molecules and loose carbon fragments dissolve or disperse in the target etching solution and are carried away. The carbonized layer gradually thins, and the catalytic effect continues, ultimately achieving thorough and directional removal layer by layer from the surface carbonized layer to the original photoresist inside.

[0056] Capillary action, also known as capillary phenomenon, refers to the phenomenon where a liquid spontaneously rises or falls in a very narrow channel (capillary tube) or porous material without external force and even against gravity. Its core driving force is the interaction between the cohesive force between liquid molecules and the adhesive force between the liquid and the solid surface.

[0057] In the embodiments of this application, the preset temperature can be 60℃~90℃, for example, the preset temperature can be 60℃, 65℃, 70℃, 80℃, 85℃, or 90℃, etc. It is understood that the catalytic effect of the carbonized layer on NO bond breaking and nucleophilic bond cleavage has a significant temperature dependence. When the temperature of the target etching solution is below 60℃, electrons in the carbonized layer sp... 2 The slow conduction rate in the network makes it difficult to effectively lower the reaction energy barrier, resulting in low peroxide decomposition and nucleophilic attack rates, and hindering the initiation of self-accelerating cycles. Furthermore, the peroxides used in this invention (such as tert-butyl hydroperoxide and cumene hydroperoxide) exhibit good thermal stability below 90°C. Above 90°C, the peroxides undergo violent self-accelerating decomposition, which not only rapidly consumes the active components but may also pose safety hazards. Therefore, this application chooses to heat the target etching solution to 60°C–90°C, a temperature range that balances etching efficiency and safety.

[0058] The preset cleaning time can be 8 to 20 minutes, for example, 8 minutes, 10 minutes, 12 minutes, 14 minutes, 16 minutes, 18 minutes, or 20 minutes. It is understood that if the cleaning time for a semiconductor structure containing carbon photoresist is less than 8 minutes, there may be issues with residual carbon layer or incomplete removal of internal photoresist. Furthermore, the target etching solution has a slight corrosive effect on sensitive materials such as copper; if the cleaning time is too long, material loss may accumulate to the point of affecting the device's electrical performance. Therefore, this application sets the cleaning time to 8 to 20 minutes, thereby balancing the device's electrical performance with the photoresist removal effect.

[0059] In applications, during the immersion of the semiconductor structure to be cleaned in the target etchant, megasonic waves can be used to assist wet etching. Megasonic waves refer to high-frequency sound waves with frequencies ranging from 0.8MHz to 3MHz. The acoustic flow effect and microjets generated by megasonic waves can push etchant molecules into the gaps in the carbonized layer, increasing the penetration rate. Furthermore, they can promptly remove reaction products from the interface while simultaneously replenishing the reaction interface with fresh etchant molecules, maintaining a consistently high reaction concentration at the interface.

[0060] S103: The semiconductor structure removed from the target etching solution is rinsed and washed in sequence, and then dried with inert gas to remove the residual target etching solution.

[0061] After cleaning the semiconductor structure with the target etching solution for a preset time, the etched semiconductor structure can be removed from the target etching solution. At this time, the semiconductor structure may contain residues of the target etching solution, small organic molecule fragments generated by photoresist depolymerization, and tiny carbon particles from the oxidation and detachment of the carbide layer. Therefore, the removed semiconductor structure can be rinsed and washed sequentially to remove the residues, obtaining the target semiconductor structure. Then, the target semiconductor structure is dried with inert gas to obtain a clean and residue-free target semiconductor structure.

[0062] In one example, rinsing a semiconductor structure removed from a target etchant refers to rinsing the semiconductor structure removed from the target etchant with isopropanol to remove residual target etchant.

[0063] Isopropanol (IPA), also known as 2-propanol, is a common secondary alcohol with the same molecular formula as propanol, but a different atomic arrangement; its chemical formula is C3H8O. Isopropanol is completely miscible in most solvents, including water, ethanol, and chloroform, and can dissolve a variety of nonpolar compounds. Therefore, this application utilizes isopropanol to dissolve residual target etching solution on the surface of semiconductor structures. It is understood that isopropanol is miscible with components such as nucleophiles and peroxides in the target etching solution of this application. Isopropanol has weak reducing properties and can undergo a mild redox reaction with residual tert-butyl hydroperoxide and other peroxides, reducing them to inert tert-butanol and water, thus reducing the risk of peroxides continuing to oxidize the metal layer during subsequent deionized water rinsing and inert gas drying steps. Isopropanol can also form hydrogen-bonded complexes with residual alkanolamine nucleophiles, reducing their basicity and reactivity, and preventing them from continuing to corrode the metal or dielectric layer in subsequent steps. Furthermore, isopropanol has low viscosity and high molecular diffusion rate, so it can quickly penetrate into the bottom of trenches and vias to replace the residual target etching solution trapped inside the microstructure of the semiconductor structure.

[0064] The rinsing temperature can be between 40℃ and 60℃, for example, 40℃, 45℃, 50℃, 55℃, or 60℃. The target etching solution in this application includes a main solvent (such as γ-butyrolactone, γ-valerolactone, N-methylpyrrolidone, or propylene carbonate) for dissolving nucleophiles and peroxides. The solubility of the main solvent in isopropanol decreases with decreasing temperature. If the rinsing temperature is below 40℃, the solubility of the main solvent in isopropanol may be low, making it difficult to effectively dissolve and displace, thus easily forming oily residues on the semiconductor structure surface. Furthermore, isopropanol has a boiling point of approximately 82.5℃. When the rinsing temperature exceeds 60℃, the evaporation rate of isopropanol is rapid, which may cause the etching solution components originally dissolved in isopropanol to re-concentrate and precipitate, forming dry spots that are more difficult to remove than the original residues. Therefore, this application sets the rinsing temperature to 40℃ to 60℃, which can balance high rinsing efficiency and good rinsing effect.

[0065] The rinsing time can be 5 to 10 minutes, for example, 5, 6, 7, 8, 9, or 10 minutes. It is understood that the nucleophiles and peroxides in the residual target etching solution need a certain amount of time to neutralize with isopropanol, reducing their activity and preventing side reactions during subsequent water rinsing. Simultaneously, since isopropanol has a weak etching effect on hard mask materials (such as TiN) in semiconductor structures, excessively long rinsing times may cause slight roughening of the hard mask material surface. Furthermore, excessively long rinsing times may also cause isopropanol to absorb moisture and carbon dioxide from the air, reducing its solubility in the target etching solution and negatively impacting the cleaning effect. Therefore, this application sets the rinsing time to 5 to 10 minutes to balance good rinsing results with protection of the semiconductor structure.

[0066] After rinsing the extracted semiconductor structure, deionized water can be used to rinse it. Deionized water (DI water) refers to pure water from which impurities in ionic form have been removed. It can be understood that deionized water and isopropanol are miscible in any proportion. A rapidly flowing water stream can displace and remove residual isopropanol from the surface and interior of the semiconductor structure, transforming the semiconductor surface from an "organic phase coating" to a "pure water phase coating."

[0067] Next, the target semiconductor structure after removing residual etchant can be dried using an inert gas. It's understood that reactive metals such as copper, aluminum, and titanium oxidize rapidly in humid air, while inert gases contain almost no oxygen or water vapor. Throughout the drying process, the surface of the target semiconductor structure is constantly surrounded by inert gas, preventing oxygen from contacting the metal surface and thus preventing oxidation. In one example, nitrogen gas can be used to dry the target semiconductor structure after removing residual etchant. This is just an illustrative example; in practical applications, other inert gases such as argon and helium can also be used.

[0068] The above-mentioned method for removing photoresist can produce at least the following unexpected technical effects:

[0069] First, a target etching solution comprising nucleophiles and peroxides is provided. The semiconductor structure to be cleaned is then immersed in the target etching solution preheated to a preset temperature, allowing the carbon-containing photoresist on the surface of the semiconductor structure to react with the target etching solution for a preset time. Since the peroxides in the target etching solution can provide oxidizing active chemical bonds, they can destroy the dense graphite-like crystal structure of the carbonized layer on the surface of the carbon-containing photoresist through oxidation, creating numerous micropores and cracks. Furthermore, since the nucleophiles can provide electron-rich nucleophilic centers, they can break the three-dimensional network of polymer chains within the photoresist into small molecule fragments soluble in the etching solution. Additionally, the carbonized layer on the surface of the carbon-containing photoresist contains numerous defect sites and unsaturated bonds, which can adsorb and enrich nucleophiles and peroxide molecules in the target etching solution, increasing the local concentration at the reaction interface, thereby improving the efficiency of nucleophilic bond breaking and the ability of oxidative deconstruction. Therefore, after cleaning the semiconductor structure with the target etching solution for the preset time, the carbon-containing photoresist on the surface of the semiconductor structure can be effectively removed. Then, the etched semiconductor structure is rinsed and washed in sequence to remove the residual target etching solution on the semiconductor structure, and the target semiconductor structure is obtained. After that, the target semiconductor structure is dried with inert gas to obtain a clean target semiconductor structure without residue.

[0070] In some exemplary embodiments, the target etching solution includes a main solvent for dissolving nucleophiles and peroxides; the main solvent is used at least to swell and permeate the carbon-containing photoresist.

[0071] In this embodiment, the semiconductor structure to be cleaned may include a patterned gate structure located on the substrate. While nucleophiles and peroxides may be liquids, excessively high purity can lead to high viscosity and poor flowability, making it difficult to uniformly wet the complex three-dimensional structure of the semiconductor surface. Therefore, the target etching solution in this application also includes a main solvent. The main solvent can dissolve the two nucleophiles and organic peroxides to uniformly disperse them throughout the system, forming a target etching solution with uniform concentration, stable properties, and good flowability. This ensures the consistency of the reaction rate at various locations on the semiconductor structure to be cleaned and allows for sufficient filling of high aspect ratio trench structures.

[0072] In applications, the main solvent of this application also possesses the ability to swell, penetrate, and dissolve macromolecules in carbon-containing photoresists. The main solvent molecules first enter the naturally occurring micro-gaps in the carbonized layer and the molecular gaps in the photoresist matrix through capillary action. The main solvent molecules then enter between the polymer chains, causing the originally tightly wound polymer chains to stretch and expand, resulting in volume expansion of the three-dimensional network. The internal stress generated by the swelling widens the gaps in the carbonized layer and simultaneously increases the distance between the cross-linking points in the photoresist matrix, forming numerous channels through which active component molecules can pass. This facilitates the breaking and depolymerization of nucleophiles and the oxidative destructive process of peroxides.

[0073] In some exemplary embodiments, the main solvent includes at least one of γ-butyrolactone, γ-valerolactone, N-methylpyrrolidone, or propylene carbonate.

[0074] γ-Butyrolactone (GBL) is an organic compound with the chemical formula C4H6O2. It is a colorless and transparent liquid used in the production of pharmaceuticals such as cyclopropylamine and pyrrolidone, and is also used in industry as a solvent, diluent, and curing agent.

[0075] γ-Valactone (GVL) is an organic compound, also known as γ-valactone ester, with the chemical formula C5H8O2. γ-Valactone is a colorless liquid and is mainly used as a solvent and medium.

[0076] N-Methylpyrrolidone (NMP) is a highly polar aprotic solvent with the chemical formula C5H9NO. It typically appears as a colorless to pale yellow, transparent, oily liquid. NMP is miscible with water in any proportion and readily soluble in most organic solvents, including diethyl ether, acetone, and halogenated hydrocarbons. It is characterized by its high boiling point, strong polarity, low viscosity, strong dissolving power, good chemical stability, and biodegradability.

[0077] Propylene carbonate (PC) is a colorless and odorless flammable liquid, also known as propylene carbonate or propylene glycol carbonate, with the chemical formula C4H6O3. It is miscible with ether, acetone, benzene, chloroform, vinyl acetate, etc., and soluble in water and carbon tetrachloride.

[0078] The primary solvent selected in this application not only possesses good swelling, deep penetration, and macromolecular dissolution capabilities, but also exhibits good compatibility with wafer materials, showing low etching rates for Poly, SiO2, SiN, TiN, NiPt, and copper metal layers. Furthermore, the primary solvent is chemically inert, exhibiting no adverse reactions with TBHP peroxide, nucleophiles, or BTA corrosion inhibitors. It also demonstrates good surface tension compatibility, enabling effective filling of high aspect ratio trench structures. Moreover, the primary solvent has a moderate boiling point, exhibiting low volatility at process temperatures ranging from 60℃ to 90℃, resulting in lower production safety risks and lower solvent loss rates.

[0079] The above embodiments can produce at least the following unexpected technical effects:

[0080] By setting reagents such as γ-butyrolactone, γ-valerolactone, N-methylpyrrolidone, or propylene carbonate as the main solvent in the target etching solution, the problems of high viscosity and poor flowability of nucleophiles and peroxides can be overcome, achieving uniform dispersion of nucleophiles and peroxides. Furthermore, the dilution effect of the main solvent can control the concentration of nucleophiles and peroxides, keeping the reaction rate at a mild and controllable level. This ensures good desizing efficiency while avoiding the risk of violent exothermic reactions that may occur when pure peroxides are mixed with pure nucleophiles.

[0081] In some exemplary embodiments, the target etching solution also includes a penetration enhancer, which is used to enhance the penetration of the target etching solution into the gaps of the carbonized layer.

[0082] In the embodiments of this application, the target of the penetration aid is the carbonized layer on the surface of the photoresist. The penetration aid can reduce the resistance of the target etching solution to entering the nanoscale gaps of the carbonized layer by improving the physicochemical properties of the target etching solution (such as surface tension, viscosity, wettability, etc.).

[0083] In some examples, the penetration enhancer includes at least one of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, or ethylene glycol dimethyl ether.

[0084] Diethylene glycol dimethyl ether (DGDE), chemical formula C6H 14 O3 has good solubility, is miscible with many inorganic salts and organic compounds, and has good stability, not easily decomposing or oxidizing.

[0085] Triethylene glycol dimethyl ether (Triglyme), chemical formula C8H 18 O4 is an ethylene glycol ether organic compound that is a colorless liquid at room temperature, soluble in water, and has high thermal stability and strong solvation ability.

[0086] Diethylene glycol dimethyl ether (DME), also known as 1,2-dimethoxyethane, is an organic compound with the chemical formula C4H. 10 O2 is a colorless and transparent liquid that is soluble in water, ethanol, and hydrocarbons. It is mainly used in polymer chemistry, electrochemistry, and boron chemistry processes. It is also used as a solvent for resins, nitrocellulose, etc., as well as a pharmaceutical extractant and an intermediate in organic synthesis.

[0087] The above embodiments can produce at least the following unexpected technical effects:

[0088] By incorporating reagents such as diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, or ethylene glycol dimethyl ether as penetration aids in the target etching solution, the penetration aid molecules can be directionally adsorbed at the etching solution-carbonized layer interface, reducing the surface tension of the liquid and allowing the target etching solution to spontaneously penetrate into the gaps. Furthermore, the penetration aid can also reduce the viscosity of the target etching solution, increase the molecular diffusion rate, reduce the flow resistance of the target etching solution in the carbonized layer gaps, and reduce the difficulty of penetrating the carbonized layer. Moreover, the penetration aid material selected in this application is miscible with other components in the target etching solution (such as the main solvent, nucleophile, peroxide, etc.), preventing phase separation or stratification of the target etching solution, thus ensuring that the target etching solution remains in a homogeneous and stable state.

[0089] In some exemplary embodiments, the target etching solution also includes an organic adsorption type corrosion inhibitor, which is used to form a dense, insoluble polymer protective film with the copper or copper alloy surface in the semiconductor structure to be cleaned through chemical adsorption, thereby blocking the target etching solution.

[0090] Although the target etching solution of this application is milder than the strong acid etching solutions in related technologies, the trace amounts of reactive oxygen species generated by the decomposition of peroxides can slowly oxidize the copper surface, and the N atoms in the alkanolamine nucleophiles have lone pairs of electrons, which can form soluble complexes with copper ions, leading to the slow dissolution of copper. Therefore, the nucleophiles and peroxides in the target etching solution of this application still pose a slight risk of corrosion to copper. Therefore, this application also adds an organic adsorbent-type corrosion inhibitor to the target etching solution. This organic adsorbent-type corrosion inhibitor contains multiple electron-rich N or S atoms, which can form stable coordinate covalent bonds with the empty d orbitals of copper atoms. The corrosion inhibitor molecules adsorbed on the copper surface will further undergo a polymerization reaction to form a dense, insoluble polymer protective film. This protective film exists only on the copper surface and does not cover the photoresist or carbonized layer surface, thus not affecting the nucleophilic bond breaking and oxidative destructive reactions of the target etching solution on the photoresist.

[0091] In some examples, the organic adsorbent corrosion inhibitor includes at least benzotriazole, methylbenzotriazole, 2-mercaptobenzothiazole, or combinations thereof.

[0092] Benzotriazole (BTA), with the chemical formula C6H5N3, is a nitrogen-containing heterocyclic compound. Benzotriazole appears as a white to yellowish-beige powder or granules, soluble in organic solvents such as toluene, chloroform, and alcohols, and slightly soluble in water. The benzotriazole molecule contains a benzene ring and a triazole ring, giving it advantages such as good antioxidant properties, excellent chemical stability, good light stability, and corrosion resistance.

[0093] Methylbenzotriazole (TTA), with the chemical formula C7H7N3, is a white to pale yellow needle-like powder. It is primarily used as a corrosion inhibitor for copper and copper alloys. In low pH media, TTA exhibits stronger corrosion inhibition than BTA and is also used in organic synthesis. Methylbenzotriazole is widely used in rust-preventive oils, circulating water treatment agents, and automotive antifreeze.

[0094] 2-Mercaptobenzothiazole (MBT), with the chemical formula C7H5NS2, is a pale yellow crystalline powder. It is mainly used as a sensitive reagent for the detection of gold, bismuth, cadmium, cobalt, mercury, nickel, lead, thallium, and zinc, and as a rubber accelerator.

[0095] The above embodiments can produce at least the following unexpected technical effects:

[0096] By incorporating reagents such as benzotriazole, methylbenzotriazole, and 2-mercaptobenzothiazole, or combinations thereof, as organic adsorption-type corrosion inhibitors into the target etching solution, these inhibitors can selectively adsorb onto the copper surface without covering the photoresist or carbide layer surface. Therefore, they do not affect the nucleophilic bond breaking and oxidative destructive reactions of the photoresist by the target etching solution, while simultaneously achieving precise protection of the copper / copper alloy. Furthermore, the organic adsorption-type corrosion inhibitors selected in this application are miscible with other components in the target etching solution (main solvent, nucleophile, peroxide, penetration enhancer), preventing phase separation or stratification in the target etching solution and ensuring that it remains in a homogeneous and stable state.

[0097] In a detailed embodiment, please refer to Figure 2 Before removing the carbon-containing photoresist from the semiconductor structure to be cleaned using the photoresist removal method of this application, a target etching solution needs to be prepared first. The target etching solution, by volume ratio, comprises: 70%–80% main solvent, 5%–10% nucleophile, 10%–15% peroxide, 3%–4% penetration enhancer, and 0.5%–1% organic adsorption-type etching inhibitor. The nucleophile, peroxide, penetration enhancer, and organic adsorption-type etching inhibitor are added to the main solvent and stirred until homogeneous to obtain the target etching solution. The target etching solution is then preheated to 60°C–90°C.

[0098] After preheating the target etching solution, the semiconductor structure to be cleaned, with carbon photoresist on its surface, is immersed in the target etching solution and cleaned for 8 to 20 minutes with the assistance of megasonic waves. After that, the semiconductor structure is removed from the target etching solution.

[0099] Next, the removed semiconductor structure can be rinsed with isopropanol to remove residual target etching solution from the semiconductor structure. Then, the rinsed semiconductor structure can be rinsed with deionized water to obtain the target semiconductor structure. Finally, the target semiconductor structure can be dried with nitrogen to obtain a clean and residue-free target semiconductor structure.

[0100] In some exemplary embodiments, this application provides a semiconductor structure that removes photoresist using the photoresist removal method described in any of the above embodiments.

[0101] In the description of this specification, references to terms such as "some embodiments," "other embodiments," and "ideal embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0102] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features of the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0103] The embodiments described above are merely examples of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application.

Claims

1. A method for removing photoresist, characterized in that, include: A non-aqueous target etching solution is provided, the target etching solution comprising a nucleophile and a peroxide; the nucleophile includes an organic ether reagent. The semiconductor structure to be cleaned, with a carbon-containing photoresist on its surface, is immersed in the target etching solution preheated to a preset temperature until the cleaning time reaches a preset duration. The nucleophile provides at least electron-rich nucleophilic centers to nucleophilically break the bonds of the network polymer in the carbon-containing photoresist into soluble small molecules. The peroxide provides at least oxidatively active chemical bonds to oxidize and deconstruct the carbonized layer in the carbon-containing photoresist, thereby disrupting its compactness. The carbonized layer on the surface of the carbon-containing photoresist is used to catalyze and enhance the efficiency of nucleophilic bond breaking and the ability of oxidative deconstruction through electron conduction and interface activation. The semiconductor structure removed from the target etching solution is rinsed and washed in sequence, and then dried with inert gas to remove the residual target etching solution.

2. The method for removing photoresist according to claim 1, characterized in that, Includes at least one of the following features: The target etching solution includes a main solvent for dissolving the nucleophile and the peroxide; the main solvent is at least used to swell and penetrate the carbon-containing photoresist. The target etching solution also includes an organic adsorption type corrosion inhibitor, which is used to form a dense, insoluble polymer protective film with the copper or copper alloy surface in the semiconductor structure to be cleaned through chemical adsorption, thereby blocking the target etching solution; The target etching solution also includes a penetration enhancer, which is used to enhance the penetration of the target etching solution into the gaps of the carbonized layer.

3. The method for removing photoresist according to claim 2, characterized in that, The main solvent includes γ-butyrolactone, γ-valerolactone, N-methylpyrrolidone, and propylene carbonate.

4. The method for removing photoresist according to claim 2, characterized in that, The penetration aid includes diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, or ethylene glycol dimethyl ether.

5. The method for removing photoresist according to claim 2, characterized in that, The organic adsorbent corrosion inhibitors include benzotriazole, methylbenzotriazole, 2-mercaptobenzothiazole, or combinations thereof.

6. The method for removing photoresist according to any one of claims 1-5, characterized in that, Includes at least one of the following features: The nucleophile further includes organic alcohol amines, wherein the organic alcohol amines include monoethanolamine, diethanolamine, triethanolamine, N,N-dimethylethanolamine, N-methylethanolamine, or combinations thereof; The organic ether reagents include ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol dimethyl ether, or combinations thereof; The peroxide includes anhydrous tert-butyl hydroperoxide or cumene hydroperoxide.

7. The method for removing photoresist according to any one of claims 1-5, characterized in that, Includes at least one of the following features: The preset temperature is 60℃~90℃; The preset duration is 8 min to 20 min; The semiconductor structure removed from the target etching solution is rinsed with isopropanol to remove residual target etching solution; wherein the rinsing temperature is 40℃~60℃ and the rinsing time is 5min~10min. Semiconductor structure after rinsing with deionized water; The target semiconductor structure is dried with nitrogen gas to remove residual target etching solution.

8. The method for removing photoresist according to any one of claims 1-5, characterized in that, During the immersion of the semiconductor structure to be cleaned in the target etching solution, megasonic-assisted wet etching is performed.

9. The method for removing photoresist according to any one of claims 1-5, characterized in that, The semiconductor structure to be cleaned includes a patterned gate structure located on a substrate.

10. A semiconductor structure, characterized in that, The photoresist is removed using the photoresist removal method according to any one of claims 1-9.

Images