A neutral metal cleaning agent for a mask plate and a method of preparing the same

Abstract

This invention relates to the field of wet electronic chemicals technology and discloses a neutral metal cleaning agent for photomasks and its preparation method, comprising: 1.8% to 2.2% free acidic phytic acid, 0.55% to 0.75% ethoxylated acetylenic glycol with a specific EO addition number (3.5), a choline hydroxide-acetic acid buffer pair to maintain a neutral environment, and ultrapure water. This invention utilizes a geometrically complementary anti-dilution desorption adsorption layer formed on the metal surface by phytic acid and ethoxylated acetylenic glycol at a specific mass ratio (2.8:1-3.2:1). This layer maintains a negative Zeta potential and provides steric hindrance during the non-equilibrium process of ultrapure water rinsing, blocking the reverse pinning of submicron particles. This adsorption layer can inhibit intergranular corrosion and pitting on the metal surface, achieving non-destructive cleaning of precision patterns.

Description

Technical Field

[0001] This invention relates to a neutral metal cleaning agent for photomasks and its preparation method, belonging to the field of wet electronic chemicals technology. Background Technology

[0002] Currently, photomasks used in semiconductor and display panel lithography processes typically consist of a quartz substrate and a chromium or molybdenum silicide metal light-shielding layer deposited on the surface. Surface cleanliness determines the yield and precision of the lithography pattern. The mainstream cleaning process in the industry generally uses strong acid or strong alkali systems to remove organic residues and particulate contaminants from the surface. Although the cleaning efficiency is high, the highly corrosive medium causes lateral etching of the metal layer and drift of critical dimensions. To solve the problems of lattice corrosion and pattern damage, technological development has shifted to using a cleaning system with a near-neutral pH value, compounded with specific chelating agents and surfactants, to remove submicron-level contaminants under gentle conditions using physical aids.

[0003] However, in neutral water-based cleaning processes, even if the cleaning agent separates contaminants from the substrate surface through chelation solubilization and wetting penetration in its undiluted state, the system still faces physicochemical stability challenges during the subsequent ultrapure water rinsing stage. When a large amount of ultrapure water replaces the high-concentration cleaning solution in a very short time, the ionic strength of the liquid phase environment decreases exponentially, causing the thickness of the double electric layer at the solid-liquid interface to expand rapidly and triggering drastic fluctuations in the Zeta potential. Existing conventional neutral cleaning formulations rely mainly on van der Waals forces or weak hydrogen bonds to maintain adsorption between surface-active molecules and the substrate. This non-specific physical bond is difficult to resist the strong ionic strength impact and solvation layer reconstruction in the early stages of rinsing, and is prone to avalanche-like desorption before the contaminants are completely washed away. Once the interfacial protective layer falls off within the critical window period, the electrostatic repulsion between the active metal surface, which has lost its steric barrier, and particulate contaminants, which are also in a low potential state, changes to van der Waals force adsorption. This leads to irreversible reverse pinning of already detached particles; even with the introduction of strong chelating components to enhance chemical detergency, it is difficult to achieve the same effect if the kinetics of the rinsing stage are ignored. For example, Chinese invention patent CN115161650B discloses a neutral metal cleaning agent for mask plates, which uses the synthetic polymer heavy metal chelating agent PATD in combination with sodium sulfate and cationic surfactants, aiming to solve the problem of silver and magnesium residues by using strong chelation. This type of technical route performs well when the cleaning solution maintains a high concentration thermodynamic equilibrium state, but in the non-equilibrium rinsing process with the intervention of ultrapure water, as the system is highly diluted, the ionic background required to maintain the stability of the chelate structure is destroyed. The macromolecular chelating agent and surfactant adsorbed at the interface desorb from the metal surface due to the sudden drop in concentration. The lack of anti-dilution locking mechanism causes the mask plate to lose its protective barrier at the moment of rinsing, and it is impossible to eliminate the risk of secondary pollution from small particles.

[0004] Therefore, how to construct a cleaning system that maintains the integrity of the interfacial adsorption structure and the stability of the potential during the non-equilibrium thermodynamic process of rapid replacement of the cleaning fluid with ultrapure water, and solve the problem of reverse adsorption of particles and secondary pollution in the rinsing stage of the neutral cleaning process, has become the technical problem to be solved by this invention. Summary of the Invention

[0005] To address the problems mentioned in the background art, the technical solution of the present invention is as follows: A neutral metal cleaning agent for photomasks, wherein the cleaning agent is a water-based composition with a pH value of 6.5 to 7.5, and is composed of the following components by weight percentage:

[0006] 1.8% to 2.2% of an interface anchoring agent, which is a free acidic phytic acid, is used to provide multidentate phosphate anchoring points on the metal surface.

[0007] 0.55% to 0.75% of a void filler, wherein the void filler is an ethoxylated derivative of 2,4,7,9-tetramethyl-5-decyn-4,7-diol, wherein the average molar number of ethylene oxide addition of the ethoxylated derivative is strictly limited to 3.5, for embedding into the molecular gaps after the adsorption of the interfacial anchoring agent.

[0008] A pH buffer pair, composed of choline hydroxide and acetic acid, is used to maintain the ionic strength background of the system; and the balance is ultrapure water; wherein the mass ratio of the interface anchoring agent to the void filler is limited to between 2.8:1 and 3.2:1. Under this ratio and the average molar number of ethylene oxide additions, the hydrophilic segments of the void filler and the uncoordinated phosphate groups of the interface anchoring agent form an intermolecular hydrogen bond network in the liquid phase that resists dilution and desorption, so that the cleaning agent maintains the negative Zeta potential of the metal surface during the non-equilibrium process of being diluted by ultrapure water.

[0009] Preferably, the choline hydroxide in the pH buffer pair is an electronic-grade raw material with a total metal cation content of less than 10 ppb, and the cleaning agent does not contain sodium ions, potassium ions, or inorganic phosphates; the molar ratio of acetic acid to choline hydroxide is determined according to the final pH value of the cleaning agent to establish a weak ionic strength environment that can maintain the adsorption configuration of the interfacial anchoring agent on the metal surface.

[0010] Preferably, the concentration of the interface anchoring agent in the cleaning agent is set to be higher than the critical micelle concentration in pure water and lower than the concentration threshold for self-association, so that the phytic acid molecules remain in a monomolecular dispersion state; the average molar addition of ethylene oxide to the void filler is limited to 3.5 based on the steric hindrance of the phytic acid molecules, so that the hydrophilic end of the void filler has the spatial geometric adaptability to penetrate the phosphate group array of the phytic acid molecules and adsorb onto the blank sites on the metal surface.

[0011] Preferably, the dynamic surface tension of the cleaning agent at 25 degrees Celsius is stable between 31 dynes per centimeter and 33 dynes per centimeter at a bubble frequency of 6 Hz; the dynamic surface tension value characterizes the dense adsorption layer formed by the void filler and interface anchor at the gas-liquid interface, which is isomorphic to the solid-liquid interface, and the adsorption layer maintains its integrity within 15 seconds after the cleaning agent is diluted with 100 times ultrapure water.

[0012] Preferably, the interface anchoring agent and the void filler exist in the liquid phase of the cleaning agent as a thermodynamically balanced binary complex; the binary complex is formed through a ripening process that eliminates the Gibbs-Marangoni effect, and its structural feature is that a stable hydrogen bond is formed between the ethoxy segment of the void filler and the hydroxyl group of the interface anchoring agent.

[0013] Preferably, the mass ratio of 2.8:1 to 3.2:1 is determined based on the ratio of the adsorption coverage area of ​​the six phosphate groups of the phytic acid molecule on the metal surface to the projected area of ​​the alkyne bond rigid center of the ethoxylated ethynylene glycol molecule; within this mass ratio range, the hydrophobic alkyne bond center of the void filler forms a hydrophobic shielding layer above the hydrophilic layer of the interface anchoring agent, which has the physical property of blocking the diffusion of dissolved oxygen in water to the metal substrate.

[0014] Preferably, the void filler has dynamic defoaming properties. When the cleaning agent is in a high shear flow field, the unsteady foam structure of the void filler can break down quickly. The dynamic defoaming properties are due to the hydrophilic-lipophilic balance value of the gemini surfactant structure of the ethoxylated acetylenic diol molecule when the average molar addition of ethylene oxide is 3.5.

[0015] Preferably, the interactions of the cleaning agent components satisfy a spatial matching index. The constraint relationship is defined by the following formula: ,in, This represents the mass ratio of the interface anchoring agent to the void filler. The average molar number of ethylene oxide additions is 3.5, and the constant 0.85 is a geometric correction factor derived from the ratio of the van der Waals radii of phytic acid molecules to those of ethoxylated acetylenic diol molecules; when the spatial matching index... When the concentration is in the range of 0.9 to 1.1, the composite adsorption film formed by the cleaning agent on the metal surface has the maximum desorption hysteresis time.

[0016] Preferably, the cleaning agent has a non-etching property that controls the change in surface roughness of the cleaned metal to within 0.1 nanometers. This property is determined by the monomolecular chemical adsorption passivation film formed on the metal surface by the interface anchoring agent. This passivation film can inhibit intergranular corrosion and pitting corrosion on the metal surface. The purity of phytic acid is greater than 98% based on chromatographic purity. Ethoxylated acetylenic glycol is a quantitative addition product of 2,4,7,9-tetramethyl-5-decyn-4,7-diol and ethylene oxide, and the addition product does not contain polyethylene glycol homopolymer impurities. The pH drift of the cleaning agent during storage under nitrogen-filled and sealed conditions is less than 0.1.

[0017] A method for preparing a neutral metal cleaning agent for photomasks, wherein the neutral metal cleaning agent for photomasks is prepared by the aforementioned neutral metal cleaning agent for photomasks.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. In the neutral metal cleaning agent of the mask plate, a geometrically complementary adsorption interface resistant to dilution impact is constructed to block the secondary pollution pathway during the rinsing stage. The mass ratio of phytic acid to ethoxylated acetylenic diol is limited to 2:1 to 4:1. The planar multidentate phosphate structure of phytic acid is used for anchoring, and the rigid central alkyne bond of ethoxylated acetylenic diol and hydrophilic segments of specific length fill the adsorption gap. Based on the geometrically complementary molecular assembly, a high-density composite adsorption film is formed on the metal surface. When the liquid phase ion intensity decreases during the ultrapure water rinsing stage, the composite adsorption film overcomes the tendency of double-layer expansion and desorption, maintains the negative Zeta potential and steric barrier on the mask plate surface, and physically continues the electrostatic repulsion between particles and the substrate. This prevents submicron-sized contaminants from being pinned to the substrate by van der Waals forces during the critical window period when the cleaning solution is replaced.

[0020] 2. Achieve non-etching in-situ passivation protection, maintaining the atomic-level integrity of critical pattern dimensions. Utilize the multi-point chelating properties of phytic acid to form a monolayer chemical adsorption passivation film on the surface of chromium or molybdenum silicide. This removes surface contaminants while physically blocking the diffusion of dissolved oxygen and active ions from the water into the metal lattice, inhibiting intergranular corrosion or pitting caused by local electrochemical potential differences. Combined with the low surface tension penetration of ethoxylated acetylene glycol, the cleaning agent does not damage the metal layer on the sidewall of the nanoscale trench to complete deep hole cleaning, ensuring that the critical dimensions of the mask plate remain stable and the surface roughness meets process requirements after multiple cleaning cycles.

[0021] 3. It possesses dynamic defoaming characteristics suitable for high-shear flow fields, eliminating cavitation damage and drying marks. It selects ethynyl diol components with specific ethoxy addition numbers to form a water-based system with phytic acid, retaining the dynamic and unsteady foaming characteristics of Gemini surfactants. Under megasonic oscillation or high-pressure spray high-shear cleaning conditions, the composition rapidly destroys the elasticity of the gas-liquid interface film, preventing the stable accumulation and regeneration of microbubbles. This rheological property eliminates the potential mechanical damage to precision patterns caused by cavitation shock waves generated by microbubble collapse, avoiding foam residue leading to micro-droplet drying marks, and meeting the engineering requirements of rapid replacement of cleaning media and residue-free drying in automated production lines. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the preparation process of the cleaning agent and the geometric complementary anti-dilution mechanism of the present invention.

[0023] Figure 2 This is a graph showing the effect of the mass ratio of the key components of this invention on the foam decay half-life and the threshold determination curve.

[0024] Figure 3 This is a timing diagram of dynamic monitoring and closed-loop calibration during the on-site deployment phase of the cleaning agent of this invention. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] This invention relates to a neutral metal cleaning agent for photomasks and its preparation method, wherein the cleaning agent has a pH value of [missing value]. to This invention relates to a water-based composition comprising free acidic phytic acid as an interface anchoring agent, a specific ethoxylated ethynyl glycol as a void filler, a choline hydroxide-acetic acid buffer pair to maintain a neutral environment, and ultrapure water. The components are pre-assembled in the liquid phase through a specific feeding sequence and thermodynamic curing process to form a binary complex with anti-dilution desorption properties. A stable negatively charged double layer and steric barrier are established on the surface of chromium or molybdenum silicide metal using a molecular spatial geometric complementarity mechanism, solving the problem of submicron particle reverse pinning caused by the sudden drop in ionic strength during the rinsing stage in neutral cleaning processes. Addressing the dilution shock effect that occurs when the cleaning solution is replaced by ultrapure water, resulting in an exponential decrease in ionic strength on the liquid film surface leading to Debye length expansion and a shift of the Zeta potential towards the isoelectric point, this invention selects free acidic phytic acid (CAS number 83-86-3) as the interface anchoring agent. The mass percentage of this phytic acid in the composition is controlled within a specified range. to Phytic acid molecules utilize their six phosphate groups to form multi-point chemisorption on the metal surface, providing a stable negatively charged substrate even at low concentrations. However, given the planar adsorption configuration of phytic acid molecules and the large intermolecular gaps, it is insufficient to completely shield van der Waals forces. Therefore, the mass percentage introduced into the system is... to The ethoxylated form of 2,4,7,9-tetramethyl-5-decyn-4,7-diol serves as a void filler. A key structural feature of this component is that the average molar number of ethylene oxide additions is strictly limited. ,choose This specific EO chain length is based on the stereochemical matching between the EO chain and the phosphate group of the phytic acid molecule. If the EO chain is too long, it will cause too much steric hindrance and prevent insertion, while if it is too short, it will not be hydrophilic enough and will lead to phase separation.

[0027] To achieve synergistic bonding of the two components on the metal surface, this invention strictly limits the mass ratio of phytic acid to ethoxylated acetylene glycol to [specific value missing]. to Within this specific range, at this particular ratio, the rigid alkyne bond center and hydrophilic side chains of the ethoxylated ethynylene glycol molecule can precisely embed into the voids after the adsorption of phytic acid macromolecules, forming a dense planar and stereocomponent adsorption layer. This complementary structure enhances the overall stability of the adsorption membrane through an intermolecular hydrogen bond network, exhibiting desorption hysteresis. During the washing process... After dilution with ultrapure water Within a two-second window, the composite adsorption membrane maintains a negative Zeta potential and steric hindrance on the metal surface, continuously shielding the adsorption of particles by van der Waals forces. The system uses choline hydroxide and acetic acid to adjust the pH, constructing an ionic background free of metal cations, ensuring electronic-grade purity and preventing the risk of gate breakdown introduced by alkali metal ions. The preparation of the cleaning agent of this invention follows a strict thermodynamic equilibrium control procedure to ensure the effective formation of molecular assemblies. The preparation process involves adding a solvent with a resistivity of not less than [missing value]. Ultrapure water, with a rotation speed of [missing information]. to With stirring, add electronic-grade solid choline hydroxide and dropwise add glacial acetic acid. Use an online pH meter to monitor and lock the pH of the system at [value missing]. Establish a stable buffer solution by adding [the following to the buffer solution] A free acidic phytic acid aqueous solution, maintained by stirring. Minutes are allowed for the phytic acid molecules to fully hydrolyze and expand; then the core assembly step is performed, increasing the stirring speed to [speed value missing]. to Slowly add EO bonus number Ethoxylated acetylenic diol, under this shear force field, acetylenic diol molecules are dispersed and inserted into the hydrated layer of phytic acid molecules. After feeding, a ripening process is performed, and the stirring speed is reduced to [missing value]. ,exist Continue stirring and maturing under constant temperature conditions minutes to This aging process, lasting for minutes, is used to eliminate the Gibbs-Marangoni effect during mixing, allowing phytic acid and acetylene glycol molecules to reach a thermodynamically balanced binary complex state through hydrogen bonds and van der Waals forces. Samples are then taken for testing at this point. The frequency of the lower bubble is The dynamic surface tension should be stable at to The interval between these intervals indicates that the adsorption configuration at the gas-liquid interface has reached saturation and no large number of micelles have formed. Finally, the drug solution passes through... The filter element is made of polytetrafluoroethylene and is packaged with nitrogen to prevent dissolved oxygen interference and particle introduction.

[0028] The thermodynamic equilibrium state of the binary composite has clear physicochemical characterization standards. The preparation process is confirmed in real time by monitoring the dynamic surface tension of the mixture. The determination procedure is as follows: 25 Under the test conditions of a bubble frequency of 6 Hz, when the dynamic surface tension of the mixture converges and stabilizes in the range of 31 dyne / cm to 33 dyne / cm, it is determined that the hydrophilic segment of the ethoxylated ethynylene glycol has been embedded in the adsorption gap of the phytic acid molecule, completing the molecular-scale ordered assembly; at this time, the Zeta potential of the system against the standard chromium surface is maintained between -25 mV and -35 mV. The concentration set in this paper is higher than the critical micelle concentration in pure water, indicating that the concentration of added phytic acid needs to be greater than 25%. The surface tension concentration isotherm in pure water shows its first inflection point concentration, corresponding to the coverage state at which the gas-liquid interface reaches monolayer saturation adsorption; spatial matching index. In the formula, the geometric correction factor of 0.85 is derived from the calibration between molecular dynamics simulations and standard chromium metal surface adsorption experiments, and its value is given by the formula. Export, The van der Waals radius projected area when the phytic acid molecule has a planar spread configuration on the metal surface. The minimum projected cross-sectional area of ​​the ethoxylated acetylenic diol molecule with an EO addition number of 3.5 was determined based on the rigid alkyne bond skeleton. 0.85 is the ratio of the geometric packing density in the saturated adsorption layer of both molecules. A correction factor constrains the mass ratio of the two materials to ensure that when the mixed system undergoes dilution shock, the interstitial filler molecules remain in the interfacial anchoring agent lattice gaps with the highest probability, rather than undergoing phase separation or micelle release. To eliminate the impact of raw material batch fluctuations or differences in production equipment shear efficiency on the final cleaning performance, the cleaning agent preparation process includes a standardized closed-loop fine-tuning procedure: after completing the basic batching and curing process, samples are taken for testing. If the dynamic surface tension at Hz is higher than 33 dyne / cm, it indicates that the void filler in the system is not fully embedded or there is local micelle aggregation. The stirring speed should be increased in increments of 100 rpm and the maturation time should be extended by 15 minutes until the index is verified to be within the standard range. If the test value is lower than 31 dyne / cm, it indicates that there is excessive free surfactant in the system. The calculated amount of phytic acid concentrate should be added to balance the adsorption sites. The procedure ensures that each batch of cleaning agent leaving the factory is in the thermodynamically stable range that can withstand the impact of 100 times dilution with ultrapure water, and does not depend on the mechanical properties of specific equipment.

[0029] Example 1: In use In the cleaning application of chromium metal layer masks in node lithography processes, due to the high-frequency use of plasma etching during the process, a large number of submicron-sized metal oxide particles accumulate on the mask surface before cleaning. These particles exhibit a similar low Zeta potential to the substrate metal layer in a conventional neutral aqueous environment, facing the challenge of reverse adsorption of particles during the rinsing stage after cleaning. When the cleaning operation enters the dilution shock stage of replacing the original solution with ultrapure water, the cleaning agent provided by this invention utilizes its pre-assembled binary composite structure to cope with the Zeta potential fluctuations caused by the sudden drop in ionic strength. In this process, the mass ratio is... to Phytic acid and EO addition number is The synergistic effect of ethoxylated ethynylene glycol allows phytic acid molecules to firmly adsorb onto the chromium metal surface, providing a basic negative charge layer, thanks to the multi-point anchoring properties of its six phosphate groups. Ethoxylated ethynylene glycol molecules, on the other hand, utilize their rigid alkyne bond center and hydrophilic segments of specific length to embed themselves in the spatial gaps left by the adsorption of phytic acid molecules. This planar-stereoscopic complementary molecular assembly mechanism allows the adsorbed layer to remain even after the system is diluted with ultrapure water. In the non-equilibrium state after doubling, the negative potential and steric barrier of the metal surface are maintained to block the path of submicron particles to be pinned in reverse by van der Waals forces. After the mask surface is treated by this cleaning process, the original metal oxide particles are removed and no intergranular corrosion or pitting defects are left on the sidewalls or surface of the precision pattern. After drying, the surface cleanliness meets the requirements of advanced processes when inspected by scanning electron microscopy.

[0030] Example 2: This example aims to verify the detergency of the neutral metal cleaning agent of the present invention in a simulated real industrial cleaning scenario and its ability to protect the microstructure of the metal surface. It also demonstrates the synergistic effect of phytic acid and ethoxylated acetylene glycol at a specific ratio and the engineering rationality of this ratio range by constructing a multi-dimensional control test system. Test platform construction and simulation conditions: The experiment was conducted on a single-blade rotary cleaning machine in a Class 10,000 cleanroom, using a surface deposited with... Thick chromium (Cr) layer An inch-sized quartz mask was used as a test sample. To simulate the harsh contamination conditions after high-frequency plasma etching, a submicron-sized alumina layer was pre-coated onto the sample surface. Particle size to The contaminated liquid contains particles, and the particles are thermally pinned by baking, with the initial surface particle count controlled at [value missing]. One to Between; Experimental design and core parameter calibration: The experiment set up five groups of samples, corresponding to the sample group of this invention, two partially missing control groups, and two out-of-range control groups. The basic formula of the cleaning agent in each group was kept consistent except for the variable, that is, all contained The free acidic phytic acid was removed, and the pH was adjusted to [value missing] using a choline hydroxide / acetic acid buffer pair. The core variable is the EO bonus. The amount of ethoxylated ethynyl glycol added was determined to construct different mass ratios of phytic acid to ethoxylated ethynyl glycol. Specific groupings and parameter settings are shown in Table 1.

[0031] Table 1: Experimental Grouping and Core Parameter Setting Table

[0032]

[0033] The cleaning process is as follows: Spray cleaning agent at high speed on each group Seconds; immediately switch to ultrapure water (UPW) for high-pressure two-fluid spray rinsing, and increase the rotation speed to ,continued Seconds; finally, high-speed nitrogen rotary drying is performed. In this process, the instant of switching from the cleaning agent to ultrapure water is the key observation window for simulating the sharp drop in ion strength and the fluctuation of Zeta potential; key data presentation and mechanism analysis: after cleaning, the number of residual particles on the surface of each group of samples was tested using a laser surface defect detection system (KLA-Tencor). The above), and the surface roughness before and after cleaning was measured using atomic force microscopy (AFM). The changes were used to assess the etching damage to the metal layer. The test results are shown in Table 2.

[0034] Table 2: Results of Cleaning Efficiency and Surface Integrity Tests

[0035]

[0036] Data shows that control group 1, containing only phytic acid, did not cause significant metal corrosion. (extremely low), but the particle removal rate is only [percentage missing]. This indicates that a single phytic acid anchoring layer cannot provide sufficient steric hindrance to counteract secondary adsorption during the rinsing stage. When ethoxylated acetylene glycol is introduced, but in a low proportion (control group 2, mass ratio...),... The removal rate was increased to This indicates that the void-filling effect is beginning to appear, but the coverage is still insufficient to form a dense barrier; in contrast, the sample group of this invention (mass ratio) )accomplish Extremely high removal rate, with only a few residual particles. This study confirmed that, at this specific ratio, ethoxylated ethynylene glycol molecules can saturately fill the adsorption gaps of phytic acid molecules, forming a geometrically complementary dense composite membrane. This composite membrane remains tightly locked to the metal surface during strong rinsing with ultrapure water and non-equilibrium processes involving drastic changes in ionic strength, maintaining effective negative potential and steric hindrance, and preventing reverse pinning of particles. It is noteworthy that when ethoxylated ethynylene glycol is added in excess to the control group 4, the mass ratio... At that time, the removal rate actually decreased to Analysis suggests that excessive surfactant molecules form micelle aggregates in the liquid phase, which not only compete for adsorption sites on the metal surface but also interfere with the orderly assembly of phytic acid molecules, resulting in impaired stability of the interfacial protective layer.

[0037] Example 3: This example combines Figures 1 to 3 This document describes a neutral metal cleaning agent for photomasks and its preparation method. Figure 1As shown, the process begins with three basic material modules: free acidic phytic acid containing multidentate phosphate anchoring points as an interface anchoring agent; a weak ionic strength background environment with a pH of 6.5 to 7.5 composed of ultrapure water and a choline-hydroxyacetic acid buffer pair; and ethoxylated acetylenic glycol with strictly controlled EO=3.5 as a void filler to provide steric hindrance filling. These components are dispersed and assembled under high shear conditions at a rotation speed of 300 rpm to 400 rpm, allowing the filler to disperse and insert into the hydration layer. This process is strictly constrained by the spatial matching index Smatch, and the mass ratio is limited to 2.8:1 to 3. Within the critical threshold of geometric complementarity of .2:1, the microstructure on the left side shows that hydrophilic segments are embedded in the gaps between phosphate groups and form an intermolecular hydrogen bond network, while the right side needs to monitor the dynamic surface tension and ensure that the value is stable between 31 dyne / cm and 33 dyne / cm at a frequency of 6 Hz. The system enters the thermodynamic ripening equilibrium stage, which aims to eliminate the Gibbs-Marangoni effect and form a stable binary complex. Finally, a geometrically complementary anti-dilution desorption adsorption layer is generated, which has the function of maintaining a negative Zeta potential and blocking the reverse pinning of submicron particles during non-equilibrium dilution with 100 times ultrapure water.

[0038] like Figure 2 As shown, the horizontal axis represents the mass ratio of phytic acid to ethoxylated acetylene glycol, with a scale range of 1.5:1 to 5.0:1. The vertical axis represents the foam dissipation half-life in seconds. The legend includes a solid line representing measured data and a dashed line representing the safety threshold. The data in the figure shows that as the mass ratio on the horizontal axis increases, the corresponding foam dissipation half-life shows an upward trend. The data points with mass ratios of 1.5:1, 2.0:1, 2.5:1, 2.8:1, 3.0:1, and 3.2:1 are all below the dashed line representing the safety threshold of 5 seconds, indicating that the defoaming performance meets the requirements. However, the data points with mass ratios of 4.0:1 and 5.0:1 are above this safety threshold. Figure 3 As shown, this process involves five interactive objects: the inspector, the cleaning agent concentrate, the supply tank, the cleaning machine, and the monitoring sensors. The sequence begins with the inspector testing the pH value, conductivity, and dynamic surface tension of the cleaning agent concentrate upon arrival. After confirming that the indicators are qualified, the cleaning agent concentrate is injected into the supply tank, the circulation filtration system is started, and the cleaning machine is sprayed with the highest working pressure. During this process, the monitoring sensors provide real-time feedback to the system on the foam decay rate and the turbidity of the microbubbles. If an abnormal condition occurs where the foam decay exceeds the threshold, the system enters a remedial branch, which involves adding a trace amount of defoaming enhancer to the supply tank and performing a 10-minute circulation mixing operation until the inspector confirms that the foam indicators are normal. Finally, the inspector establishes a process parameter lookup table based on the stable data, marking the completion of the cleaning machine calibration and its readiness for production.

[0039] Example 4: This example aims to systematically optimize the ratio of key components in the cleaning agent and establish an optimal working window to address the engineering risks of decreased cleaning efficiency or material corrosion caused by drift in formulation parameters. This example uses a verification experiment incorporating gradient concentration variables to quantitatively analyze the impact of changes in the mass ratio of phytic acid to ethoxylated ethynylene glycol on cleaning efficiency and surface integrity. To clarify the optimal mixing ratio of phytic acid and ethoxylated ethynylene glycol, this example employs an orthogonal experimental design method, with a fixed phytic acid concentration... and pH value Under the baseline conditions, a concentration gradient of ethoxylated ethynylene glycol was set. The test sample was a chromium metal layer mask that had undergone standard photoresist stripping process, with residual organic residues and metal ions from photoresist ashing on the surface. Ethoxylated ethynylene glycol (EO addition number: The addition amount of each is set as follows: , , , and The corresponding mass ratios of phytic acid to ethoxylated acetylene glycol are respectively , , , and .

[0040] The cleaning process was carried out in the same single-blade rotary cleaning machine, with process parameters consistent with Example 2. Evaluation indicators for the cleaning effect included the removal rate of organic residues (calculated by measuring changes in surface carbon content using total reflectance X-ray fluorescence spectrometry (TXRF)) and the pitting density of the metal surface (counted by dark-field microscopy to determine the number of pits per unit area). Experimental data showed that with the increase of ethoxylated acetylene glycol addition, the removal rate of organic residues first increased and then tended to stabilize. When the mass ratio increased from... Reduce to At that time, the removal rate was from Upgraded to This indicates that the addition of ethoxylated acetylene glycol effectively enhances the wetting and solubilizing ability of the cleaning solution on hydrophobic organic residues, and at a mass ratio of... To achieve the best synergistic effect, continue increasing the concentration of ethoxylated acetylene glycol to a mass ratio of [value missing]. At that time, the removal rate remained at The cleaning capacity was close to saturation, with no improvement observed. However, regarding surface integrity, the pitting density exhibited a non-linear change with increasing ethoxylated acetylene glycol concentration, remaining relatively stable at a mass ratio of [missing value]. to Within this range, the pitting density remains at an extremely low level, less than This indicates that the passivation film formed by phytic acid maintains good compactness with the assistance of ethoxylated acetylene glycol, even when the mass ratio is reduced to [value missing]. At that time, the pitting density rose sharply to Excessively high concentrations of surfactant molecules form a dense adsorption layer on the metal surface. While this is beneficial for the removal of organic matter, it also hinders the effective contact between phytic acid molecules and the metal surface, leading to an increase in local defects in the passivation film and subsequently causing pitting corrosion. Considering both cleaning efficiency and surface protection capability, the optimal mass ratio of phytic acid to ethoxylated acetylene glycol is determined to be within the range of [range missing]. to Within this range, the cleaning agent can achieve efficient removal of organic residues while minimizing the risk of pitting corrosion on metal surfaces. The establishment of this ratio range is based on a comprehensive balance between detergency and corrosion resistance, providing reliable parameter basis for the engineering application of the cleaning agent.

[0041] Example 5: Before applying the neutral metal cleaning agent of this invention to a large-scale production line, a crucial on-site pre-deployment calibration procedure is performed to ensure that the rheological properties of the cleaning agent in specific piping systems and spraying equipment match the design values, avoiding process deviations caused by equipment differences. The core of this procedure is to perform in-situ verification and fine-tuning of the dynamic defoaming performance of the cleaning agent under high shear flow fields. The prepared cleaning agent concentrate is injected into the supply tank of the cleaning machine to be used, the machine's circulation filtration system is started, and the pressure of the spray arm is set to the highest working pressure of this process section. Under continuous spray circulation, an online foam height detection sensor or optical turbidimeter installed on the return liquid line is used to monitor the foam layer decay rate and bubble content in the return liquid in real time. If the monitoring data shows that the foam decay half-life exceeds a preset threshold, the process is initiated. If the turbidity caused by microbubbles in the reflux liquid is consistently higher than the baseline value, it indicates that the shear field strength of the current equipment exceeds the inhibition capacity of the defoaming component in the original formula of the cleaning agent.

[0042] To address the above situation, a fine-tuning procedure needs to be initiated, adding a small amount of defoaming synergist to the supply tank. This synergist is a homologue of ethoxylated acetylene glycol in the original formula, but with a slightly lower hydrophilic-lipophilic balance (HLB) value. The addition process must follow the principle of small, rapid steps, meaning that each addition should not exceed the total liquid volume. And after supplementation, perform no less than The mixture is cyclically mixed for minutes until the monitored foam deterioration rate returns to the standard range, ensuring that the cleaning agent can maintain an ideal low-foam state in spray equipment with different geometries and pressure conditions, eliminating the potential risks of cavitation damage and drying marks.

[0043] Example 6: In the pre-deployment calibration and model building procedures for standardized systems used in specific application scenarios, to ensure the performance consistency of the cleaning agent on the actual production line, a strict incoming material inspection and process matching procedure was established. Key physicochemical indicators of each batch of arriving cleaning agent concentrate were verified, including pH value, conductivity, and dynamic surface tension at a specific frequency. For dynamic surface tension, the detection frequency was set to [missing information]. The acceptable range is locked within to The structural integrity of the surfactant-phytic acid assembly was verified between these parameters.

[0044] To address the differences in spray arm geometry and pressure distribution across different cleaning machines, a flow field adaptability calibration procedure was implemented. Before the first cleaning, the spray pressure and rotation speed were adjusted, and the foam height and decay rate in the return liquid were monitored. A high-speed camera was used to capture the spreading morphology of the liquid film on the rotating substrate, and the liquid film rupture time and coverage were calculated. If the liquid film rupture time was lower than a set threshold, it indicated that excessive local shear force damaged the adsorption layer, requiring fine-tuning to reduce the spray pressure or increase the rotation speed to optimize liquid film stability. Finally, based on the calibration data, a process parameter lookup table for specific cleaning machines was constructed, indicating the optimal combination of spray pressure, rotation speed, and cleaning time under different operating conditions, ensuring that the actual operating parameters of the cleaning agent on any cleaning machine are within the optimal working window.

[0045] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A neutral metal cleaning agent for photomasks, characterized in that, The cleaning agent is a water-based composition with a pH value between 6.5 and 7.5, and consists of the following components by weight percentage: 1.8% to 2.2% of an interface anchoring agent, which is a free acidic phytic acid, is used to provide multidentate phosphate anchoring points on the metal surface. 0.55% to 0.75% of a void filler, wherein the void filler is an ethoxylated derivative of 2,4,7,9-tetramethyl-5-decyn-4,7-diol, wherein the average molar number of ethylene oxide addition of the ethoxylated derivative is strictly limited to 3.5, for embedding into the molecular gaps after the adsorption of the interfacial anchoring agent. A pH buffer pair, composed of choline hydroxide and acetic acid, is used to maintain the ionic strength background of the system; and the balance is ultrapure water; wherein the mass ratio of the interface anchoring agent to the void filler is limited to between 2.8:1 and 3.2:

1. Under this ratio and the average molar number of ethylene oxide additions, the hydrophilic segments of the void filler and the uncoordinated phosphate groups of the interface anchoring agent form an intermolecular hydrogen bond network in the liquid phase that resists dilution and desorption, so that the cleaning agent maintains the negative Zeta potential of the metal surface during the non-equilibrium process of being diluted by ultrapure water.

2. The neutral metal cleaning agent for photomasks according to claim 1, characterized in that, The choline hydroxide in the pH buffer pair is an electronic-grade raw material with a total metal cation content of less than 10 ppb, and the cleaning agent does not contain sodium ions, potassium ions, or inorganic phosphates; the molar ratio of acetic acid to choline hydroxide is determined according to the final pH value of the cleaning agent to establish a weak ionic strength environment that can maintain the adsorption configuration of the interfacial anchoring agent on the metal surface.

3. The neutral metal cleaning agent for photomasks according to claim 1, characterized in that, The concentration of the interface anchoring agent in the cleaning agent is set to be higher than the critical micelle concentration in pure water and lower than the concentration threshold for self-association, so that the phytic acid molecules remain in a monomolecular dispersion state; the average molar addition of ethylene oxide to the void filler is limited to 3.5 based on the steric hindrance of the phytic acid molecules, so that the hydrophilic end of the void filler has the spatial geometric adaptability to penetrate the phosphate group array of phytic acid molecules and adsorb onto the blank sites on the metal surface.

4. The neutral metal cleaning agent for photomasks according to claim 1, characterized in that, The dynamic surface tension of the cleaning agent at 25 degrees Celsius is stable between 31 dynes per centimeter and 33 dynes per centimeter at a bubble frequency of 6 Hz. The dynamic surface tension value characterizes the dense adsorption layer formed by the void filler and interface anchor at the gas-liquid interface, which is isomorphic to the solid-liquid interface. This adsorption layer maintains its integrity for 15 seconds after the cleaning agent is diluted with 100 times ultrapure water.

5. A neutral metal cleaning agent for photomasks according to claim 1, characterized in that, The interface anchoring agent and the void filler exist in the liquid phase of the cleaning agent as a thermodynamically balanced binary complex. The binary complex is formed through a curing process that eliminates the Gibbs-Marangoni effect, and its structural feature is that a stable hydrogen bond is formed between the ethoxy segment of the void filler and the hydroxyl group of the interface anchoring agent.

6. A neutral metal cleaning agent for photomasks according to claim 1, characterized in that, The mass ratio of 2.8:1 to 3.2:1 is determined based on the ratio of the adsorption coverage area of ​​the six phosphate groups of phytic acid molecules on the metal surface to the projected area of ​​the rigid alkyne bond center of the ethoxylated ethynylene glycol molecule. Within this mass ratio range, the hydrophobic alkyne bond center of the void filler forms a hydrophobic shielding layer above the hydrophilic layer of the interface anchoring agent. This hydrophobic shielding layer has the physical property of blocking the diffusion of dissolved oxygen in water to the metal substrate.

7. A neutral metal cleaning agent for photomasks according to claim 1, characterized in that, The void filler has dynamic defoaming properties. When the cleaning agent is in a high shear flow field, the unsteady foam structure of the void filler can break down quickly. The dynamic defoaming properties are due to the hydrophilic-lipophilic balance value of the gemini surfactant structure of the ethoxylated ethynyl glycol molecule when the average molar number of ethylene oxide addition is 3.

5.

8. A neutral metal cleaning agent for photomasks according to claim 1, characterized in that, The interactions of the cleaning agent components satisfy a spatial matching index. The constraint relationship is defined by the following formula: ,in, This represents the mass ratio of the interface anchoring agent to the void filler. The average molar number of ethylene oxide additions is 3.5, and the constant 0.85 is a geometric correction factor derived from the ratio of the van der Waals radii of phytic acid molecules to those of ethoxylated acetylenic diol molecules; when the spatial matching index... When the concentration is in the range of 0.9 to 1.1, the composite adsorption film formed by the cleaning agent on the metal surface has the maximum desorption hysteresis time.

9. A neutral metal cleaning agent for photomasks according to claim 1, characterized in that, The cleaning agent possesses non-etching properties that control the change in surface roughness of the cleaned metal to within 0.1 nanometers. This property is determined by the monomolecular chemical adsorption passivation film formed on the metal surface by the interface anchoring agent. This passivation film can inhibit intergranular corrosion and pitting corrosion on the metal surface. The purity of phytic acid is greater than 98% based on chromatographic purity. Ethoxylated acetylenic glycol is a quantitative addition product of 2,4,7,9-tetramethyl-5-decyn-4,7-diol and ethylene oxide, and this addition product does not contain polyethylene glycol homopolymer impurities. The pH drift of the cleaning agent during storage under nitrogen-filled and sealed conditions is less than 0.

1.

10. A method for preparing a neutral metal cleaning agent for a photomask, characterized in that, The method for preparing the neutral metal cleaning agent for photomasks is as described in claim 1.

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