A method for removing photoresist based on supercritical carbon dioxide and cosolvent

Abstract

The application discloses a method for removing photoresist based on supercritical carbon dioxide and cosolvent, and relates to the fields of semiconductor manufacturing technology and supercritical fluid engineering technology. The method comprises the following steps: fixing a wafer to be removed; mixing carbon dioxide and a cosolvent and increasing the temperature and pressure to a supercritical state to form a mixed cleaning system; contacting the mixed cleaning system with the fixed wafer to dissolve photoresist on the wafer surface; and after the photoresist is dissolved, performing at least two stages of pressure relief to make the dissolved photoresist gasify and be discharged with carbon dioxide. Through the two-stage pressure relief strategy, the method avoids photoresist redeposition and microstructure damage caused by single-stage rapid pressure relief, realizes lossless removal of high-aspect-ratio microstructures, and has a photoresist removal rate of greater than 99.9% and a microstructure collapse rate of less than 0.5%. Moreover, the method is green and environmentally friendly, and is suitable for large-scale application of advanced semiconductor processes.

Description

Technical Field

[0001] This invention belongs to the fields of semiconductor manufacturing technology and supercritical fluid engineering technology, specifically relating to a method for removing adhesive based on the synergistic action of supercritical carbon dioxide and co-solvent. Background Technology

[0002] In advanced semiconductor manufacturing processes (especially at 7nm and below), efficient and non-destructive removal of photoresist after etching is a crucial step in ensuring device yield and reliability. Traditional wet photoresist removal processes commonly use highly polar organic solvents such as acetone and N-methylpyrrolidone (NMP). While these solvents possess some solubility, they suffer from high toxicity, poor biodegradability, and high wastewater treatment costs. More seriously, these solvents readily undergo coordination reactions with metal interconnect materials such as Al, Cu, and TiN, leading to etching rates exceeding 1nm / min. They can also penetrate porous low-k media, causing dielectric constant shifts exceeding 10%, severely impacting device electrical performance. On the other hand, although dry plasma ashing technology avoids liquid residue, its high-energy particle bombardment and local high temperature (>200°C) can easily cause damage to the gate sidewalls of planar FinFETs or three-dimensional GAA transistors, as well as cracking of 3D NAND stepped structures due to thermal expansion mismatch. At the same time, in microstructures with high aspect ratio (>10:1), the diffusion of active free radicals is restricted, resulting in a residual adhesive rate of more than 5% in the bottom corner area, which often requires additional wet cleaning, creating process redundancy and increasing the risk of contamination.

[0003] To balance environmental friendliness and microstructure compatibility, supercritical carbon dioxide (scCO2) has been introduced into the field of photoresist removal due to its advantages such as low surface tension, high diffusivity, non-toxicity, and easy recyclability. Existing technologies have attempted to combine scCO2 with co-solvents to enhance its solubility in mainstream phenolic resin-diazonaphthoquinone (Novolac-DNQ) photoresists. For example, Chinese invention patent CN1246888C discloses a method for removing photoresist and photoresist residues from semiconductors using supercritical carbon dioxide, achieving stripping through the interaction of chemicals with the photoresist; Chinese invention patent CN102346381A proposes using high-temperature, high-pressure water and hydrogen peroxide to assist scCO2 in oxidative stripping.

[0004] However, the existing scCO2 photoresist removal technology still has systemic defects: First, the solubility parameters of pure scCO2 are mismatched with those of Novolac-DNQ photoresists, resulting in slow dissolution kinetics that are difficult to meet the requirements of mass production cycle time; second, the introduction of the co-solvent lacks scientific design rules based on compatibility and glass transition temperature (Tg) control, which can easily lead to microphase separation in the mixed system or cause glass transition blockage on the surface of the photoresist layer, thus reducing the removal efficiency; third, the temperature and pressure control strategy is crude: too fast a pressure increase rate can easily cause the photoresist surface to become dense, forming undissolved cores, while too fast a pressure release can cause the dissolved polymer to be redeposited on the wafer surface due to supersaturation; at the same time, the existing system has not designed a dynamic flow field adapted to the low viscosity and high compressibility of scCO2 fluid characteristics, which can easily generate mass transfer dead zones or gas blockages in high aspect ratio structures, resulting in a removal uniformity standard deviation of more than 15%; fourth, the process endpoint generally relies on fixed time control, which cannot respond to changes in dissolution kinetics caused by photoresist thickness, structural morphology, or batch differences, and can easily lead to over-cleaning or under-cleaning. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for photoresist removal based on the synergistic effect of supercritical carbon dioxide and co-solvent, in order to solve the technical problem of photoresist redeposition and microstructure damage caused by uncontrollable pressure relief when removing high aspect ratio microstructure photoresist in the existing supercritical carbon dioxide photoresist removal method.

[0006] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a method for degumming based on the synergistic effect of supercritical carbon dioxide and co-solvent, comprising the following steps: S1, Fix the wafer to be de-adhesive removed; S2 involves mixing carbon dioxide with a co-solvent and heating and pressurizing the mixture to a supercritical state to form a mixed cleaning system. S3, the mixed cleaning system is brought into contact with the fixed wafer to dissolve the photoresist on the wafer surface; S4. After the photoresist has dissolved, perform at least two stages of depressurization to allow the dissolved photoresist to be vaporized and discharged with carbon dioxide.

[0007] A further improvement of the present invention is that the co-solvent in S2 is mixed with carbon dioxide in a micro-atomized form, and the volume fraction of the co-solvent in the mixed cleaning system is 0.1%-10%.

[0008] A further improvement of the present invention is that the cosolvent in S2 is selected from at least one of isopropanol, ethanol, acetone, ethyl acetate, polyethylene glycol 200 and N,N-dimethylacetamide.

[0009] A further improvement of the present invention is that, when the photoresist to be removed is a phenolic resin-diazonaphthoquinone system positive photoresist, the co-solvent is isopropanol with a volume fraction of 2%-5%.

[0010] A further improvement of the present invention is that, before the mixed cleaning system described in S3 comes into contact with the wafer, the temperature of the mixed cleaning system is increased to the target cleaning parameters at a rate of 1-3°C / min and the pressure is increased to a rate of 1-1.5MPa / min.

[0011] A further improvement of the present invention is that, when the hybrid cleaning system described in S3 comes into contact with the wafer, the hybrid cleaning system dynamically flows over the wafer surface in the form of a circulating flow field, and the average flow velocity of the circulating flow field is 0.25-0.4 m / s; and during the process of dynamically flowing over the wafer surface, the wafer rotates horizontally at a speed of 8-15 rpm.

[0012] A further improvement of the present invention is that, in S3, the photoresist is completely dissolved by monitoring the ultraviolet absorption signal from the photoresist in the mixed cleaning system: when the rate of change of the decrease rate of the ultraviolet absorption signal is less than 5% for three consecutive sampling periods, the photoresist is determined to have completely dissolved.

[0013] A further improvement of the present invention is that the two-stage depressurization in S4 includes: the depressurization rate of the first stage is 2-3 MPa / min, and the depressurization rate of the second stage is 0.5-1.5 MPa / min.

[0014] A further improvement of the present invention is that the rate of the second-stage pressure relief is selected according to the aspect ratio of the microstructure on the wafer: when the aspect ratio is ≥10:1, the rate of the second-stage pressure relief is 0.5-1.0 MPa / min; when the aspect ratio is <10:1, the rate of the second-stage pressure relief is 1.0-1.5 MPa / min.

[0015] A further improvement of the present invention is that, after S4, a recovery operation is included, specifically: the discharged gas is subjected to gas-liquid separation, the separated liquid co-solvent is recovered, and the separated gaseous carbon dioxide is dried and purified before being recycled.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for photoresist removal based on the synergistic use of supercritical carbon dioxide and a co-solvent. By designing at least two stages of depressurization, the dissolved photoresist is steadily vaporized and discharged in stages with carbon dioxide. Compared to existing single-stage rapid depressurization or uncontrollable depressurization rates, this method effectively avoids the redeposition of dissolved polymers on the wafer surface due to supersaturation caused by sudden pressure changes. It also significantly reduces impact damage to high aspect ratio microstructures, increasing the microstructure integrity rate to over 99% and controlling the residual photoresist area ratio to below 0.01%. This method eliminates the need for additional wet or dry post-cleaning processes, simplifying the process flow. The number of depressurization stages and the rate of each stage can be flexibly adjusted according to the wafer structure characteristics, exhibiting good parameter reproducibility and a batch-to-batch photoresist removal uniformity standard deviation of less than 5%. Furthermore, due to the two-stage depressurization strategy, the carbon dioxide vaporization process is stable and controllable, avoiding wafer thermal stress deformation caused by rapid depressurization. The metal layer corrosion rate can be reduced to below 0.1 nm / min, and the dielectric constant drift of low-k dielectrics is less than 2%. This method has a wide process window and strong equipment compatibility, making it suitable for both small-scale optimization in the laboratory and large-scale continuous operation on semiconductor production lines, thus showing good prospects for industrialization.

[0017] Furthermore, by depressurizing in at least two stages to allow the dissolved photoresist to be vaporized and discharged with carbon dioxide, it is possible to effectively suppress the oversaturation of the dissolved photoresist layer due to a sudden drop in pressure and its re-deposition on the wafer surface. At the same time, it avoids the collapse damage caused by single-stage rapid depressurization to the high aspect ratio microstructure, ensuring the integrity of the microstructure and the surface cleanliness during the depressurization process.

[0018] Furthermore, by monitoring both ultraviolet absorption signals and particle count, the dissolution endpoint can be determined in real time and objectively. This avoids over-cleaning (increased metal corrosion) or under-cleaning (residual adhesive area ratio >0.1%) caused by traditional fixed-time cleaning. The cleaning time control accuracy can be improved to within ±5%, and the standard deviation of adhesive removal consistency between batches is less than 3%. At the same time, subjective judgment errors are eliminated, ensuring that each batch of wafers reaches a consistent cleanliness standard.

[0019] Furthermore, different second-stage decompression rates are selected based on the aspect ratio of the microstructures on the wafer, matching the decompression rate with the mechanical fragility of the microstructures. A slower decompression rate for high aspect ratio structures avoids sidewall stress concentration and pattern collapse caused by pressure gradients, while a faster rate for low aspect ratio structures increases process cycle time. SEM verification shows that using this strategy, the collapse rate of microstructures with an aspect ratio ≥10:1 is less than 0.5%, while the overall decompression time is more than 20% shorter than a uniformly slow decompression rate. Attached Figure Description

[0020] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely illustrative to aid in understanding the invention and do not specifically limit the shapes and proportions of the components.

[0021] Figure 1 This is a schematic diagram of a method for degumming based on the synergistic action of supercritical carbon dioxide and cosolvent according to the present invention; Figure 2 This is a schematic diagram of a process flow for degumming based on the synergistic action of supercritical carbon dioxide and co-solvent in an embodiment of the present invention. Detailed Implementation

[0022] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0023] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0024] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0025] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0026] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0027] The technical solution of the present invention will be described in detail below with reference to specific steps. It should be noted that the preferred process parameters and system configurations described in this section are only for the purpose of helping to understand the specific implementation of the present invention and are not intended to limit the scope of protection of the present invention.

[0028] like Figure 1 and Figure 2 As shown, this invention provides a method for degumming based on the synergistic effect of supercritical carbon dioxide and co-solvent, comprising the following steps: S1: Wafer Fixing The wafer to be stripped of photoresist is fixed in place. In one specific fixing method, the etched wafer can be fixed on a stage within a high-pressure cleaning chamber using a vacuum chuck. To prevent oxidation, after fixing, the chamber is pre-charged with high-purity carbon dioxide to 3-5 MPa, then vented to 0.05 MPa, and this cycle is repeated 1-2 times to reduce the oxygen content in the chamber to below 1%. Simultaneously, based on the target process node and product technical requirements, process boundary conditions such as wafer size, photoresist type, and microstructure aspect ratio are determined; and based on compatibility indicators such as solubility parameters and phase diagram information, the co-solvent system and its ratio are pre-determined to meet the requirements for controllable dissolution kinetics.

[0029] S2: Constructing a hybrid cleaning system Carbon dioxide and a co-solvent are mixed and heated to a supercritical state to form a mixed cleaning system. Specifically, carbon dioxide is first introduced into a mixer, while the co-solvent is sprayed into the mixer in a micro-atomized form. After the two are uniformly mixed, the temperature and pressure are increased to a supercritical state. The volume fraction of the co-solvent in the mixed cleaning system is preferably 0.1%-10%, and it can be selected from at least one of isopropanol, ethanol, acetone, ethyl acetate, polyethylene glycol 200, or N,N-dimethylacetamide.

[0030] S3: Dissolve the photoresist First, the mixed cleaning system is adjusted to the target cleaning parameters, and then the adjusted mixed cleaning system is brought into contact with the wafer to dissolve the photoresist. The target cleaning parameters refer to the temperature and pressure conditions required for the mixed cleaning system to effectively dissolve the photoresist. These parameters vary depending on the type of photoresist. For example, when the photoresist to be removed is a phenolic resin-diazonaphthoquinone system positive photoresist, 2%-5% isopropanol by volume is preferred as a co-solvent, and a pressure of 12.5-15 MPa and a temperature of 50-60°C are used as the target cleaning parameters. The preferred adjustment method is to increase the temperature at a rate of 1-3°C / min and the pressure at a rate of 1-1.5 MPa / min to reach the target cleaning parameters. During contact, the mixed cleaning system preferably flows dynamically across the wafer surface in the form of a circulating flow field, with an average flow rate controlled at 0.25-0.4 m / s, while the wafer rotates horizontally at a speed of 8-15 rpm. To achieve the aforementioned circulating flow field and temperature / pressure control, the following system can be used: a high-pressure cleaning chamber (forged as a single piece using 316L stainless steel or Hastelloy C-276, with an inner wall electropolished to Ra<0.4μm, capable of withstanding pressures from 0-30MPa), a mixer (whose outlet is connected to the chamber inlet via a programmable temperature / pressure control pipeline), a porous rectifier plate located above the wafer, and an annular suction port below it. This suction port is connected to a variable frequency magnetically coupled circulation pump via a circulation pipeline, forming a counter-current flow field of upward spraying and downward suction. During cleaning, the temperature fluctuation within the chamber is less than ±0.5℃, and the pressure fluctuation is less than ±0.1MPa. Furthermore, in S3, the dissolution of the photoresist is determined by monitoring the ultraviolet absorption signal from the photoresist in the mixed cleaning system and the number of stripped particles: when the rate of change of the decrease rate of the ultraviolet absorption signal is less than 5% for three consecutive sampling periods (the rate of change refers to the absolute value of the relative deviation of the decrease rate of the ultraviolet absorption signal in two adjacent sampling periods), and the number of stripped particles is stable for three consecutive sampling periods, the photoresist is determined to have been completely dissolved.

[0031] S4: Two-stage pressure relief After the photoresist has dissolved, at least two stages of depressurization are performed to allow the dissolved photoresist to be vaporized and discharged with carbon dioxide. Specifically, a two-stage back pressure valve control is preferred: the first stage depressurization rate is 2-3 MPa / min, decreasing to 3 MPa; the second stage depressurization rate is 0.5-1.5 MPa / min, decreasing to 0.2 MPa. The second stage depressurization rate is selected based on the aspect ratio of the microstructure on the wafer: 0.5-1.0 MPa / min is selected when the aspect ratio is ≥10:1; and 1.0-1.5 MPa / min is selected when the aspect ratio is <10:1. During depressurization, the cavity temperature decrease rate does not exceed 3 °C / min. This depressurization process promotes the smooth vaporization of supercritical carbon dioxide, carrying away the dissolved photoresist and effectively inhibiting the redeposition of the dissolved photoresist layer.

[0032] Following S4, a recovery operation is also included, specifically: the discharged gas undergoes gas-liquid separation to recover the separated liquid co-solvent, and the separated gaseous carbon dioxide is dried and purified before being recycled. Specifically, the discharged mixture first enters a condenser at 2-5°C (i.e., the co-solvent recovery unit) for primary separation, recovering more than 90% of the co-solvent and photoresist enriched phase; the gaseous carbon dioxide is then pressurized by an oil-free compressor, dehydrated by a 3A molecular sieve drying tower, and has organic matter removed by a coconut shell activated carbon adsorption tank, and finally passes through a 0.01μm PTFE filter to remove particles, restoring the carbon dioxide purity to greater than 99.99% and the metal ion content to less than 10ppb, with a total recovery rate of greater than 90%, and is recycled back to step S1.

[0033] Verification and Results After cleaning, the photoresist removal effect can be verified by using XPS to detect the residual resist area ratio, laser particle detector to measure particle increment, electrochemical AFM to measure metal corrosion rate, AFM to measure surface roughness increment, and SEM to statistically analyze the high aspect ratio microstructure pattern collapse rate. Verification shows that wafers treated using the method of this invention exhibit a photoresist removal rate greater than 99.9% and a high aspect ratio microstructure collapse rate less than 0.5%, meeting the requirements of advanced processes.

[0034] This invention is based on the synergistic regulation of phase behavior and dissolution kinetics in the scCO2-cosolvent ternary system. Combined with a programmable gradient temperature and pressure path, a two-stage pressure relief strategy, and online UV-particle dual-signal endpoint determination, it enables continuous completion of permeation, swelling, dissolution, separation, and recovery within the same process platform. This achieves high-precision and stable control over degumming efficiency, surface cleanliness, microstructure integrity, and solvent recycling rate, while also considering closed-loop management of metal corrosion inhibition and particulate contamination, meeting the engineering requirements for mass production of advanced processes at 7nm and below. Specifically, it includes the following key technical points: First, establish rules for the selection and combination of cosolvents based on objective compatibility indicators. The cosolvent system includes at least one of alcohols, esters, ketones, carbonates, and nitriles, and can be further combined with auxiliary components such as proton ionic liquids, oligomers, and organic amines to improve the solubility parameter matching, hydrogen bond network strength, and interfacial tension characteristics between photoresist, cosolvent, and scCO2, forming a stable and processable mixed cleaning system.

[0035] Second, the process mainly follows the "scCO2-co-solvent contact swelling-circulating flow field driven dissolution-two-stage depressurization and separation-online monitoring and endpoint determination-solvent closed-loop circulation and recovery" route. For wafer cleaning of advanced processes of 7nm and below, a precise and green resist removal path is provided: carbon dioxide and co-solvent are mixed and heated and pressurized to construct a hybrid cleaning system. After adjusting to the target parameters through a programmable temperature and pressure path, the system contacts the wafer, allowing the hybrid cleaning system to dynamically flow over the wafer surface in the form of a circulating flow field. After online UV-particle dual signal endpoint determination, two-stage depressurization is performed, and the discharged gas is separated into gas and liquid to recover the solvent.

[0036] Third, online monitoring and stage switching criteria are introduced, using ultraviolet absorption, particle counting, and their linked signals to determine the dissolution endpoint, achieving repeatable control of the pressure reduction rate and segmentation settings. When the rate of change of the ultraviolet absorption signal decrease is less than 5% over three consecutive sampling periods, and the number of peeled particles remains stable over three consecutive sampling periods, the photoresist is determined to have completely dissolved, thereby reducing the impact of process fluctuations on the consistency of surface cleanliness and avoiding over-cleaning or under-cleaning.

[0037] Fourth, a mapping relationship between "process parameters - dissolution kinetics - surface cleanliness" is constructed. By adjusting parameters such as temperature, pressure, type and volume fraction of co-solvent, circulation flow rate and pressure reduction program, predictable design of degumming efficiency, initial dissolution rate, surface particle increment and microstructure protection can be achieved.

[0038] Fifth, it achieves closed-loop circulation and recycling of CO2 and co-solvents, meeting the requirements of green manufacturing and regulatory compliance. The ultra-clean surface obtained by this invention can be used as a pretreatment standard for subsequent thin film deposition or bonding processes, and is suitable for multiple application scenarios such as logic chip FinFET / GAA, 3D NAND memory devices, MEMS deep cavity structures and wafer-level packaging TSV, meeting the comprehensive requirements of high yield, low damage and zero emissions for mass production of advanced processes at 7nm and below.

[0039] It should be noted that the above steps use objective compatibility indicators and process trends as criteria, without limiting specific values ​​or timeframes; the scCO2 conditions only need to maintain a supercritical state and meet the requirements for wafer microstructure integrity and cleaning uniformity. The cosolvent recovery unit and carbon dioxide recovery and purification unit are used for phase separation, deep purification, and reuse of the discharged mixed medium, thereby achieving a closed-loop cycle of cosolvent and CO2. This module can operate continuously or in parallel with the degumming and depressurization processes, thus completing resource regeneration without affecting the production line cycle time.

[0040] The present invention also provides an ultra-clean wafer surface obtained by the above-described photoresist removal method, wherein the ultra-clean wafer surface has the following characteristics: the area ratio of residual photoresist on the surface is less than 0.01%, the thickness of the organic carbon redeposition layer does not exceed the XPS detection limit (0.1 nm); the increase in surface particles (particle size 0.16 μm and above) is less than 10 counts / wafer, the metal ion contamination is less than 10 ppb; the corrosion rate of metal wiring (Al / Cu / TiN) is less than 0.1 nm / min, the dielectric constant drift of low-k dielectric is less than 2%; the surface roughness increase is less than 0.2 nm; the high aspect ratio microstructure has no visible collapse, sidewall damage or bridging defects, and the pattern integrity reaches more than 99% as detected by SEM.

[0041] This invention also provides an application of the aforementioned ultra-clean wafer surface, which is suitable for various scenarios including: post-gate cleaning of FinFET and GAA structures in logic chips, post-resist stripping after step etching of 3D NAND memory devices, cleaning of TSV structures in wafer-level packaging (WLP), post-release cleaning of MEMS deep cavity structures, and surface activation before bonding of heterogeneous integrated chips. Furthermore, the ultra-clean surface can serve as a standard pretreatment for subsequent thin film deposition or bonding processes, combined with the production line MES system and particle online monitoring system to construct an intelligent cleaning closed loop for mass production of 7nm and below advanced processes, meeting the requirements of high yield, low damage, and zero emissions in green manufacturing.

[0042] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0043] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" represents weight percentage, "parts" represents parts by weight, and "ratio" represents weight proportion.

[0044] Example 1 This embodiment provides a method for resist removal based on the synergistic effect of supercritical carbon dioxide and co-solvent, specifically for the resist removal process of phenolic resin-diazonaphthoquinone (DNQ) positive photoresist on a 12-inch wafer after etching, including the following steps: 1) Wafer specifications and photoresist specifications Using a 12-inch (300mm) wafer, EUV lithography and dry etching processes have been completed. MIR701-29CP type positive photoresist remains on the surface, with a photoresist layer thickness of 40nm. The aspect ratio of the microstructure after etching is 5:1, which is a FinFET structure.

[0045] 2) Equipment and Cosolvent Selection The high-pressure cleaning chamber is forged from a single piece of 316L stainless steel, with the inner wall electropolished to a surface roughness Ra=0.3μm. It has an effective diameter of 330mm and a volume of 15L. The sealing structure uses a combination of a metal spiral wound gasket (316L / Graphite, 99.1% graphite purity) and a perfluoroether rubber O-ring. Helium mass spectrometry analysis showed a leakage rate of 8×10⁻⁶. -6 Pa·m 3 / s. The vacuum chuck has an adsorption orifice diameter of 0.6 mm, a wafer warpage of 0.05 mm, and a negative pressure setting of -0.05 MPa. The co-solvent is 5% isopropanol (IPA) with a purity of 99.999%.

[0046] 3) Construction of pre-purging and hybrid cleaning system 99.999% pure CO2 is introduced into the high-pressure cleaning chamber, pre-charged to 4 MPa, and then allowed to stand. The pressure is then rapidly reduced to 0.05 MPa, and this cycle is repeated twice to reduce the oxygen content in the chamber to below 1%. After pre-purging, CO2 is introduced into the mixer, and a co-solvent is sprayed simultaneously to achieve a volume fraction of 5% in the mixed cleaning system. When the temperature in the mixer reaches 40°C and the pressure reaches 8 MPa, a programmable temperature and pressure path is used to coordinately adjust the heating rate at 2°C / min and the pressure rate at 1.2 MPa / min to achieve the target operating conditions of 12.5 MPa and 60°C. This mixed cleaning system is then introduced into the high-pressure cleaning chamber, completing the cleaning system setup.

[0047] 4) Dynamic dissolution and degumming A variable frequency magnetic coupling circulation pump with a rated flow rate of 100 L / min and a head of 1.2 MPa was used. A porous rectifier plate with a 1.0 mm aperture and a 50% porosity was placed 12 mm away from the wafer to form a vertical countercurrent circulation flow field with a flow velocity of 0.3 m / s. During the cleaning process, the temperature fluctuation in the high-pressure cleaning chamber was less than ±0.5℃ and the pressure fluctuation was less than ±0.1 MPa. Simultaneously, the wafer rotated horizontally at a uniform speed of 12 rpm. During the cleaning process, the absorbance of the DNQ groups in the system was detected in real time using an ultraviolet absorption sensor, and the stripped particles were monitored using a particle counter. The cleaning endpoint was determined when the rate of decrease of the ultraviolet signal changed by 1.8% over three consecutive sampling periods and the particle count stabilized at 8 counts / mL.

[0048] 5) Two-stage pressure relief After cleaning, a two-stage back pressure valve system was used for depressurization: the first stage reduced the pressure from 12.5 MPa to 3 MPa at a rate of 2.5 MPa / min, and the second stage reduced the pressure from 3 MPa to 0.2 MPa at a rate of 1.5 MPa / min. Verification using SEM at 100kx magnification showed that the FinFET structure did not collapse.

[0049] 6) Solvent recovery After depressurization, the discharged mixture is first recovered through a condenser at 2°C to obtain a 91.2% IPA and photoresist mixture. The remaining gaseous CO2 is pressurized to 9MPa and 75°C by an oil-free compressor, then dehydrated to a moisture content of 0.8ppm using a 3A molecular sieve drying tower. Organic matter is then removed by a coconut shell activated carbon adsorption column (automatic regeneration is initiated when the online TOC monitoring reaches 9ppm, with a regeneration temperature of 200°C and nitrogen purging). Finally, particles are removed using a 0.01μm PTFE filter. The recovered CO2 has a purity of 99.99%, a metal ion content of 8ppb, and a recycling rate of 92%.

[0050] 7) Verification of cleaning effect Surface residue: XPS measurements showed that the atomic percentage of carbon on the surface was 1.2%, and SEM optical detection showed that the area of ​​residue was less than 0.01%. Metal ion contamination: Na was measured by ICP-MS + K + Ca 2+ The total amount is 6 ppb; Particulate contamination: The Surfscan SP7 measured an increase of 6 counts per piece of particles larger than 0.16 μm. Metal corrosion: The corrosion rate of Cu wiring measured by EC-AFM was 0.07 nm / min; Surface roughness: The surface roughness Ra increment measured by AFM was 0.1 nm; Dielectric properties: The dielectric constant drift of the low-k dielectric was measured to be 1.2% by the mercury probe CV method. Structural integrity: SEM observation of 100 FinFET structures revealed no identifiable collapses, sidewall damage, or bridging defects.

[0051] Example 2 This embodiment provides a method for resist removal based on the synergistic effect of supercritical carbon dioxide and co-solvent, specifically for the resist removal process of phenolic resin-diazonaphthoquinone (DNQ) positive photoresist on a 12-inch wafer after etching, including the following steps: 1) Wafer specifications and photoresist specifications Using a 12-inch (300mm) wafer, EUV lithography and dry etching processes have been completed. MIR701-29CP type positive photoresist remains on the surface, with a photoresist layer thickness of 35nm. The aspect ratio of the microstructure after etching is 8:1, which is a FinFET structure.

[0052] 2) Equipment and Cosolvent Selection The high-pressure cleaning chamber is forged from a single piece of 316L stainless steel, with the inner wall electropolished to a surface roughness Ra=0.3μm. It has an effective diameter of 330mm and a volume of 15L. The sealing structure uses a combination of a metal spiral wound gasket (316L / Graphite, 99.1% graphite purity) and a perfluoroether rubber O-ring. Helium mass spectrometry analysis showed a leakage rate of 8×10⁻⁶. -6 Pa·m 3 / s. The vacuum chuck has an adsorption orifice diameter of 0.6 mm, a wafer warpage of 0.05 mm, and a negative pressure setting of -0.05 MPa. The co-solvent is 2% isopropanol (IPA) with a purity of 99.999%.

[0053] 3) Construction of pre-purging and hybrid cleaning system 99.999% pure CO2 is introduced into the high-pressure cleaning chamber, pre-charged to 4 MPa, and then allowed to stand. The pressure is then rapidly reduced to 0.05 MPa, and this cycle is repeated twice to reduce the oxygen content in the chamber to below 1%. After pre-purging, CO2 is introduced into the mixer, and a co-solvent is sprayed simultaneously to achieve a 2% volume fraction of co-solvent in the mixed cleaning system. When the temperature in the mixer reaches 40°C and the pressure reaches 8 MPa, a programmable temperature and pressure path is used to coordinately adjust the heating rate at 1°C / min and the pressure rate at 1 MPa / min to achieve the target operating conditions of 15 MPa and 50°C. This mixed cleaning system is then introduced into the high-pressure cleaning chamber, completing the cleaning system setup.

[0054] 4) Dynamic dissolution and degumming A variable frequency magnetic coupling circulation pump with a rated flow rate of 100 L / min and a head of 1.2 MPa was used. A porous rectifier plate with a 1.0 mm aperture and a 50% porosity was placed 12 mm away from the wafer to form a vertical countercurrent circulation flow field with a flow velocity of 0.25 m / s. During the cleaning process, the temperature fluctuation in the high-pressure cleaning chamber was less than ±0.5℃ and the pressure fluctuation was less than ±0.1 MPa. Simultaneously, the wafer rotated horizontally at a uniform speed of 8 rpm. During the cleaning process, the absorbance of the DNQ groups in the system was detected in real time using an ultraviolet absorption sensor, and the stripped particles were monitored using a particle counter. The cleaning endpoint was determined when the rate of decrease of the ultraviolet signal was 2.1% over three consecutive sampling periods and the particle count stabilized at 6 counts / mL.

[0055] 5) Two-stage pressure relief After cleaning, a two-stage back pressure valve system was used for depressurization: the first stage reduced the pressure from 15 MPa to 3 MPa at a rate of 2 MPa / min, and the second stage reduced the pressure from 3 MPa to 0.2 MPa at a rate of 1.0 MPa / min. Verification using SEM at 100kx magnification showed that the FinFET structure did not collapse.

[0056] 6) Solvent recovery After depressurization, the discharged mixture is first recovered through a condenser at 3°C ​​to obtain a 90.5% IPA and photoresist mixture. The remaining gaseous CO2 is pressurized to 9 MPa and 75°C by an oil-free compressor, then dehydrated to a moisture content of 0.9 ppm using a 3A molecular sieve drying tower. Organic matter is then removed by a coconut shell activated carbon adsorption column (automatic regeneration is initiated when the online TOC monitoring reaches 9 ppm, with a regeneration temperature of 200°C and nitrogen purging). Finally, particles are removed using a 0.01 μm PTFE filter. The recovered CO2 has a purity of 99.99%, a metal ion content of 7 ppb, and a recycling rate of 91%.

[0057] 7) Verification of cleaning effect Surface residue: XPS measurements showed that the atomic percentage of carbon on the surface was 1.3%, and SEM optical detection showed that the area of ​​residue was less than 0.01%. Metal ion contamination: Na was measured by ICP-MS + K + Ca 2+ The total amount is 5 ppb; Particulate contamination: The Surfscan SP7 measured an increase of 8 counts per piece of particles larger than 0.16 μm. Metal corrosion: The corrosion rate of Cu wiring measured by EC-AFM was 0.06 nm / min; Surface roughness: The surface roughness Ra increment measured by AFM was 0.12 nm; Dielectric properties: The dielectric constant drift of the low-k dielectric was measured to be 1.0% by the mercury probe CV method. Structural integrity: SEM observation of 100 FinFET structures revealed no identifiable collapses, sidewall damage, or bridging defects.

[0058] Example 3 This embodiment provides a method for resist removal based on the synergistic effect of supercritical carbon dioxide and co-solvent. Specifically, it is a resist removal process for phenolic resin-diazonaphthoquinone (DNQ) positive photoresist in high aspect ratio microstructures on a 12-inch wafer after etching, including the following steps: 1) Wafer specifications and photoresist specifications Using a 12-inch (300mm) wafer, EUV lithography and dry etching processes have been completed. MIR701-29CP type positive photoresist remains on the surface, with a photoresist layer thickness of 50nm. The aspect ratio of the microstructure after etching is 15:1, and it is a GAA structure.

[0059] 2) Equipment and Cosolvent Selection The high-pressure cleaning chamber is integrally forged from Hastelloy C-276 alloy, with the inner wall electropolished to a surface roughness Ra=0.3μm. It has an effective diameter of 330mm and a volume of 15L. The sealing structure uses a combination of a metal spiral wound gasket (316L / Graphite, 99.1% graphite purity) and a perfluoroether rubber O-ring. Helium mass spectrometry analysis showed a leakage rate of 8×10⁻⁶. -6 Pa·m 3 / s. The vacuum chuck has an adsorption orifice diameter of 0.6 mm, a wafer warpage of 0.05 mm, and a negative pressure setting of -0.05 MPa. The co-solvent is 3.5% isopropanol (IPA) with a purity of 99.999%.

[0060] 3) Construction of pre-purging and hybrid cleaning system 99.999% pure CO2 is introduced into the high-pressure cleaning chamber, pre-charged to 4 MPa, and then allowed to stand. The pressure is then rapidly reduced to 0.05 MPa, and this cycle is repeated twice to reduce the oxygen content in the chamber to below 1%. After pre-purging, CO2 is introduced into the mixer, and a co-solvent is sprayed simultaneously to achieve a volume fraction of 3.5% in the mixed cleaning system. When the temperature in the mixer reaches 40°C and the pressure reaches 8 MPa, a programmable temperature and pressure path is used to coordinately adjust the heating rate at 3°C / min and the pressure rate at 1.5 MPa / min to achieve the target operating conditions of 13.5 MPa and 55°C. This mixed cleaning system is then introduced into the high-pressure cleaning chamber, completing the cleaning system setup.

[0061] 4) Dynamic dissolution and degumming A variable frequency magnetic coupling circulation pump with a rated flow rate of 100 L / min and a head of 1.2 MPa was used. A porous rectifier plate with a 1.0 mm aperture and a 50% porosity was placed 12 mm away from the wafer to form a vertical countercurrent circulation flow field with a flow velocity of 0.4 m / s. During the cleaning process, the temperature fluctuation in the high-pressure cleaning chamber was less than ±0.5℃ and the pressure fluctuation was less than ±0.1 MPa. Simultaneously, the wafer rotated horizontally at a uniform speed of 15 rpm. During the cleaning process, the absorbance of the DNQ groups in the system was detected in real time using an ultraviolet absorption sensor, and the stripped particles were monitored using a particle counter. The cleaning endpoint was determined when the rate of decrease of the ultraviolet signal changed by 2.5% over three consecutive sampling periods and the particle count stabilized at 9 counts / mL.

[0062] 5) Two-stage pressure relief After cleaning, a two-stage back pressure valve system was used for depressurization: the first stage reduced the pressure from 13.5 MPa to 3 MPa at a rate of 3 MPa / min, and the second stage reduced the pressure from 3 MPa to 0.2 MPa at a rate of 0.8 MPa / min. Verification using SEM at 100kx magnification showed that the GAA structure did not collapse.

[0063] 6) Solvent recovery After depressurization, the discharged mixture is first recovered through a 5°C condenser to obtain a 91.8% IPA and photoresist mixture. The remaining gaseous CO2 is pressurized to 10 MPa and 80°C by an oil-free compressor, then dehydrated to a moisture content of 0.7 ppm using a 3A molecular sieve drying tower, followed by removal of organic matter using a coconut shell activated carbon adsorption column, and finally particle removal using a 0.01 μm PTFE filter. The recovered CO2 has a purity of 99.995%, a metal ion content of 6 ppb, and a recycling rate of 93%.

[0064] 7) Verification of cleaning effect Surface residue: XPS measurements showed that the atomic percentage of carbon on the surface was 1.1%, and SEM optical detection showed that the area of ​​residue was less than 0.01%. Metal ion contamination: Na was measured by ICP-MS + K + Ca 2+ The total amount is 4 ppb; Particulate contamination: The Surfscan SP7 measured an increase of 9 counts per piece of particles larger than 0.16 μm. Metal corrosion: The corrosion rate of Cu wiring measured by EC-AFM was 0.05 nm / min; Surface roughness: The surface roughness Ra increment measured by AFM was 0.18 nm; Dielectric properties: The dielectric constant drift of the low-k dielectric was measured to be 0.8% by the mercury probe CV method; Structural integrity: SEM observation of 100 GAA structures revealed no identifiable collapses, sidewall damage, or bridging defects, indicating that the nanosheet cantilever structures were intact.

[0065] Example 4 This embodiment provides a method for resist removal based on the synergistic effect of supercritical carbon dioxide and co-solvent, specifically for the resist removal process of chemically amplified positive photoresist (CAR) on a 12-inch wafer after etching, including the following steps: 1) Wafer specifications and photoresist specifications Using a 12-inch (300mm) wafer, EUV lithography and dry etching processes have been completed. SPR955CM type chemical amplification positive photoresist remains on the surface, with a photoresist layer thickness of 40nm. The aspect ratio of the microstructure after etching is 5:1, which is a FinFET structure.

[0066] 2) Equipment and Cosolvent Selection The high-pressure cleaning chamber is forged from a single piece of 316L stainless steel, with the inner wall electropolished to a surface roughness Ra=0.3μm. It has an effective diameter of 330mm and a volume of 15L. The sealing structure uses a combination of a metal spiral wound gasket (316L / Graphite, 99.1% graphite purity) and a perfluoroether rubber O-ring. Helium mass spectrometry analysis showed a leakage rate of 8×10⁻⁶. -6 Pa·m 3 / s. The vacuum chuck has an adsorption orifice diameter of 0.6 mm, a wafer warpage of 0.05 mm, and a negative pressure setting of -0.05 MPa. The co-solvent is 1% acetone (Ac) with a purity of 99.999%.

[0067] 3) Construction of pre-purging and hybrid cleaning system 99.999% pure CO2 is introduced into the high-pressure cleaning chamber, pre-charged to 4 MPa, and then allowed to stand. The pressure is then rapidly reduced to 0.05 MPa, and this cycle is repeated twice to reduce the oxygen content in the chamber to below 1%. After pre-purging, CO2 is introduced into the mixer, and a co-solvent is sprayed simultaneously to achieve a 1% volume fraction of co-solvent in the mixed cleaning system. When the temperature in the mixer reaches 40°C and the pressure reaches 8 MPa, a programmable temperature and pressure path is used to coordinately adjust the heating rate at 2°C / min and the pressure rate at 1.2 MPa / min to achieve the target operating conditions of 13.5 MPa and 60°C. This mixed cleaning system is then introduced into the high-pressure cleaning chamber, completing the cleaning system setup.

[0068] 4) Dynamic dissolution and degumming A variable frequency magnetic coupling circulation pump with a rated flow rate of 100 L / min and a head of 1.2 MPa was used. A porous rectifier plate with a 1.0 mm aperture and a 50% opening ratio was placed 12 mm away from the wafer to form a vertical countercurrent circulation flow field with a flow velocity of 0.3 m / s. During the cleaning process, the temperature fluctuation in the high-pressure cleaning chamber was less than ±0.5℃ and the pressure fluctuation was less than ±0.1 MPa. Simultaneously, the wafer rotated horizontally at a uniform speed of 12 rpm. During the cleaning process, a UV absorption sensor was used to detect the characteristic UV absorption signal from the chemically amplified photoresist in the mixed cleaning system in real time, and a particle counter was used to monitor the stripped particles. The cleaning endpoint was determined when the rate of decrease of the UV signal changed by 1.8% over three consecutive sampling periods and the particle count stabilized at 8 counts / mL.

[0069] 5) Two-stage pressure relief After cleaning, a two-stage back pressure valve system was used for depressurization: the first stage reduced the pressure from 13.5 MPa to 3 MPa at a rate of 2.5 MPa / min, and the second stage reduced the pressure from 3 MPa to 0.2 MPa at a rate of 1.5 MPa / min. Verification by SEM at 100kx magnification showed that the FinFET structure did not collapse.

[0070] 6) Solvent recovery After depressurization, the discharged mixture is first recovered through a condenser at 2°C to obtain a 90.7% Ac and photoresist mixture. The remaining gaseous CO2 is pressurized to 9 MPa and 75°C by an oil-free compressor, then dehydrated to a moisture content of 0.8 ppm using a 3A molecular sieve drying tower. Organic matter is then removed by a coconut shell activated carbon adsorption column (automatic regeneration is initiated when the online TOC monitoring reaches 9 ppm, with a regeneration temperature of 200°C and nitrogen purging). Finally, particles are removed using a 0.01 μm PTFE filter. The recovered CO2 has a purity of 99.99%, a metal ion content of 8 ppb, and a recycling rate of 92%.

[0071] 7) Verification of cleaning effect Surface residue: XPS measurements showed that the atomic percentage of carbon on the surface was 1.3%, and SEM optical detection showed that the area of ​​residue was less than 0.01%. Metal ion contamination: Na was measured by ICP-MS + K + Ca 2+ The total amount is 6 ppb; Particulate contamination: The Surfscan SP7 measured an increase of 6 counts per piece of particles larger than 0.16 μm. Metal corrosion: The corrosion rate of Cu wiring measured by EC-AFM was 0.05 nm / min; Surface roughness: The surface roughness Ra increment measured by AFM was 0.12 nm; Dielectric properties: The dielectric constant drift of the low-k dielectric was measured to be 1.3% by the mercury probe CV method; Structural integrity: SEM observation of 100 FinFET structures revealed no identifiable collapses, sidewall damage, or bridging defects.

[0072] Example 5 This embodiment provides a method for resist removal based on the synergistic effect of supercritical carbon dioxide and co-solvent, specifically for the resist removal process of chemically amplified positive photoresist (CAR) on a 12-inch wafer after etching, including the following steps: 1) Wafer specifications and photoresist specifications Using a 12-inch (300mm) wafer, EUV lithography and dry etching processes have been completed. SPR955CM type chemical amplification positive photoresist remains on the surface, with a photoresist layer thickness of 40nm. After etching, the microstructure has an aspect ratio of 8:1, which is a FinFET structure.

[0073] 2) Equipment and Cosolvent Selection The high-pressure cleaning chamber is forged from a single piece of 316L stainless steel, with the inner wall electropolished to a surface roughness Ra=0.3μm. It has an effective diameter of 330mm and a volume of 15L. The sealing structure uses a combination of a metal spiral wound gasket (316L / Graphite, 99.1% graphite purity) and a perfluoroether rubber O-ring. The helium mass spectrometry leakage rate is 8×10⁻⁶. -6 Pa·m 3 / s. Vacuum chuck suction orifice diameter 0.6mm, wafer warpage 0.05mm, negative pressure set to... 0.05 MPa. The co-solvent used is 10% acetone (Ac) with a purity of 99.999%.

[0074] 3) Construction of pre-purging and hybrid cleaning system 99.999% pure CO2 is introduced into the high-pressure cleaning chamber, pre-charged to 4 MPa, allowed to stand, and then rapidly discharged to 0.05 MPa. This cycle is repeated twice to reduce the oxygen content in the chamber to below 1%. After pre-purging, CO2 is introduced into the mixer, and a co-solvent is sprayed simultaneously to ensure that the volume fraction of the co-solvent in the mixed cleaning system reaches 10%. When the temperature in the mixer reaches 40℃ and the pressure reaches 8 MPa, the target operating conditions of 13.5 MPa and 60℃ are achieved through a programmable temperature and pressure path, with a heating rate of 2℃ / min and a pressure increase rate of 1.2 MPa / min. The mixed cleaning system is then introduced into the high-pressure cleaning chamber, completing the construction of the cleaning system.

[0075] 4) Dynamic dissolution and degumming A variable frequency magnetically coupled circulation pump with a rated flow rate of 100 L / min and a head of 1.2 MPa was used. A porous rectifier plate with a 1.0 mm aperture and a 50% opening ratio was placed 12 mm away from the wafer to form a vertical countercurrent circulation flow field with a flow velocity of 0.3 m / s. During the cleaning process, the temperature fluctuation in the high-pressure cleaning chamber was less than ±0.5℃ and the pressure fluctuation was less than ±0.1 MPa. Simultaneously, the wafer rotated horizontally at a uniform speed of 12 rpm. During the cleaning process, a UV absorption sensor was used to detect the characteristic UV absorption signal from the chemically amplified photoresist in the mixed cleaning system in real time, and a laser particle counter was used to monitor the stripped particles. The cleaning endpoint was determined when the rate of decrease of the UV signal changed by 1.6% over three consecutive sampling periods and the particle count stabilized at 7 counts / mL.

[0076] 5) Two-stage pressure relief After cleaning, a two-stage back pressure valve was used to control the depressurization: the first stage reduced the pressure from 13.5 MPa to 3 MPa at a rate of 2.5 MPa / min; the second stage reduced the pressure from 3 MPa to 0.2 MPa at a rate of 1.2 MPa / min. Verification by SEM at 100kx magnification showed that the FinFET structure exhibited no collapse or sidewall damage.

[0077] 6) Solvent recovery After depressurization, the discharged mixture is first recovered through a 2°C condenser to obtain a 91.5% acetone and photoresist mixture. The remaining gaseous CO2 is pressurized to 9 MPa and 75°C by an oil-free compressor, dehydrated to a moisture content of 0.7 ppm by a 3A molecular sieve drying tower, then has organic matter removed by a coconut shell activated carbon adsorption column, and finally has particulate matter removed by a 0.01 μm PTFE filter. The recovered CO2 has a purity of 99.99%, a metal ion content of 6 ppb, and a recycling rate of 92.1%.

[0078] 7) Verification of cleaning effect Surface residue: XPS analysis showed that the atomic percentage of carbon on the surface was 0.9%, and SEM optical analysis showed that the area of ​​residue was less than 0.01%. Metal ion contamination: ICP MS measured Na + K + Ca 2+ The total amount is 5 ppb; Particulate contamination: The Surfscan SP7 measured an increase of 6 counts per piece of particles larger than 0.16 μm. Metal corrosion: The corrosion rate of Cu wiring measured by EC-AFM was 0.06 nm / min; Surface roughness: The surface roughness Ra increment measured by AFM was 0.13 nm; Dielectric properties: The dielectric constant drift of the low-k dielectric was measured to be 1.1% by the mercury probe CV method; Structural integrity: SEM observation of 100 FinFET structures showed no collapse, no sidewall damage, and no bridging defects.

[0079] Comparative Example 1 This comparative example uses the conventional NMP wet desizing process as a reference for existing technology. The specific steps are as follows: 1) Wafer specifications and photoresist specifications Using the same 12-inch (300mm) wafer as in Example 1, EUV lithography and dry etching processes have been completed. MIR701-29CP type positive photoresist remains on the surface with a thickness of 40nm. The aspect ratio of the microstructure after etching is 5:1, which is a FinFET structure.

[0080] 2) Degumming process The wafer was immersed in a cleaning tank containing N-methylpyrrolidone (NMP) with a purity of 99.5% at a cleaning temperature of 80°C for 30 minutes. It was then rinsed with deionized water (DIW) in three stages of overflow, each stage lasting 5 minutes. Finally, the surface liquid was removed by spin drying (SRD) at 3000 rpm for 60 seconds.

[0081] 3) Verification and comparative analysis of cleaning effect: Surface residue: XPS measured the atomic percentage of carbon on the surface to be 3.2%, and SEM optical detection showed that the area ratio of residue was 0.35%, with residue of adhesive layer present at the bottom corner of the microstructure; Metal ion contamination: Na was measured by ICP-MS + K + Ca 2+ The total amount is 45 ppb; Particulate contamination: The Surfscan SP7 measured an increase of 15 counts per piece of particles larger than 0.16 μm. Metal corrosion: Under the combined effects of immersion in 80°C NMP and subsequent rinsing with deionized water, the equivalent corrosion rate of Cu wiring surface due to solvent oxidation and electrochemical action, as measured by EC-AFM, was approximately 0.15 nm / min. Surface roughness: The surface roughness Ra increment measured by AFM was 0.45 nm; Dielectric properties: The dielectric constant drift of the low-k dielectric was measured to be 1.8% by the mercury probe CV method; Structural integrity: SEM observation of 100 FinFET structures revealed that one structure exhibited pattern collapse (1% collapse rate), and two structures showed sidewall bridging defects (2% bridging defect rate). Solvent residue: GC-MS measured the NMP residue on the wafer surface to be 8.5 ng / cm². 2 .

[0082] In summary, Examples 1-5 of this invention employ a synergistic supercritical carbon dioxide and co-solvent method for resist removal, achieving efficient and non-destructive cleaning under mild conditions: after cleaning, the atomic percentage of residual resist on the surface is ≤1.3%, the area ratio of residual resist is <0.01%, the total metal ion contamination is ≤6 ppb, the increase in particles larger than 0.16 μm is ≤9 counts / wafer, the Cu etching rate is ≤0.07 nm / min, the surface roughness Ra increase is ≤0.18 nm, the dielectric constant drift of the low-k dielectric is ≤1.3%, and no microstructure collapse or bridging defects are observed. In contrast, Comparative Example 1 uses a traditional NMP wet resist removal method. Although the process is simple, the area ratio of residual resist after cleaning reaches 0.35%, the total metal ion contamination is as high as 45 ppb, the particle increase is 15 counts / wafer, the Cu etching rate reaches 0.15 nm / min, the surface roughness increase is 0.45 nm, the dielectric constant drift is 1.8%, and 1% structural collapse and 2% bridging defects appear. Furthermore, NMP solvent (8.5 ng / cm³) remains on the wafer surface. 2 As can be seen, the method of the present invention is significantly superior to conventional wet processes in terms of thoroughness of resist removal, control of metal / particle contamination, microstructure protection, and environmental friendliness, and is especially suitable for resist removal requirements of high aspect ratio and fine semiconductor structures.

[0083] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for synergistic degumming based on supercritical carbon dioxide and co-solvent, characterized in that, Includes the following steps: S1, Fix the wafer to be de-adhesive removed; S2 involves mixing carbon dioxide with a co-solvent and heating and pressurizing the mixture to a supercritical state to form a mixed cleaning system. S3, the mixed cleaning system is brought into contact with the fixed wafer to dissolve the photoresist on the wafer surface; S4. After the photoresist has dissolved, perform at least two stages of depressurization to allow the dissolved photoresist to be vaporized and discharged with carbon dioxide.

2. The method for degumming based on the synergistic effect of supercritical carbon dioxide and co-solvent according to claim 1, characterized in that, The co-solvent mentioned in S2 is mixed with carbon dioxide in a micro-atomized form, and the volume fraction of the co-solvent in the mixed cleaning system is 0.1%-10%.

3. The method for degumming based on the synergistic effect of supercritical carbon dioxide and co-solvent according to claim 1, characterized in that, The co-solvent mentioned in S2 is selected from at least one of isopropanol, ethanol, acetone, ethyl acetate, polyethylene glycol 200, and N,N-dimethylacetamide.

4. The method for degumming based on the synergistic effect of supercritical carbon dioxide and co-solvent according to claim 3, characterized in that, When the photoresist to be removed is a phenolic resin-diazonaphthoquinone system positive photoresist, the co-solvent is isopropanol with a volume fraction of 2%-5%.

5. The method for degumming based on the synergistic effect of supercritical carbon dioxide and co-solvent according to claim 1, characterized in that, Before the hybrid cleaning system described in S3 comes into contact with the wafer, the temperature of the hybrid cleaning system is increased to the target cleaning parameters at a rate of 1-3℃ / min and the pressure is increased to a rate of 1-1.5MPa / min.

6. The method for synergistic degumming based on supercritical carbon dioxide and co-solvent according to claim 1, characterized in that, When the hybrid cleaning system described in S3 comes into contact with the wafer, the hybrid cleaning system dynamically flows over the wafer surface in the form of a circulating flow field with an average flow velocity of 0.25-0.4 m / s; and during the dynamic flow over the wafer surface, the wafer rotates horizontally at a speed of 8-15 rpm.

7. The method for degumming based on the synergistic effect of supercritical carbon dioxide and co-solvent according to claim 1, characterized in that, In S3, the photoresist is completely dissolved by monitoring the ultraviolet absorption signal from the photoresist in the mixed cleaning system: when the rate of decrease of the ultraviolet absorption signal is less than 5% for three consecutive sampling periods, the photoresist is determined to have completely dissolved.

8. The method for degumming based on the synergistic effect of supercritical carbon dioxide and co-solvent according to claim 1, characterized in that, The two-stage depressurization described in S4 includes: the first stage depressurization rate is 2-3 MPa / min, and the second stage depressurization rate is 0.5-1.5 MPa / min.

9. The method for degumming based on the synergistic effect of supercritical carbon dioxide and co-solvent according to claim 8, characterized in that, The rate of the second-stage depressurization is selected based on the aspect ratio of the microstructure on the wafer: when the aspect ratio is ≥10:1, the rate of the second-stage depressurization is 0.5-1.0 MPa / min; when the aspect ratio is <10:1, the rate of the second-stage depressurization is 1.0-1.5 MPa / min.

10. The method for synergistic degumming based on supercritical carbon dioxide and co-solvent according to claim 1, characterized in that, The process after S4 includes a recovery operation, specifically: gas-liquid separation of the discharged gas, recovery of the separated liquid co-solvent, and drying and impurity removal of the separated gaseous carbon dioxide before recycling.

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