A mixed acid medicine liquid concentration linkage precision liquid supplement control method

Abstract

This invention discloses a precise replenishment control method for mixed acid solutions linked to concentration. The method involves cyclically sampling and automatically potentiometrically titrating a mixed acid solution containing hydrofluoric acid and sulfuric acid in a process tank. Based on the sampling timescale, titration completion timescale, and processing load, discharge volume, and water replenishment volume during the analysis period, the titration concentration of the two acids is reconstructed over time. A cross-response matrix characterizing the main response and cross-dilution response of the two stock solutions is constructed. The replenishment volume of the stock solution is jointly calculated, the intermediate concentration trajectory for different replenishment sequences is predicted, and pre-replenishment, mixing lock, and corrective replenishment are performed. This invention relates to the field of automatic replenishment control technology for mixed acid solutions. This precise replenishment control method for mixed acid solutions linked to concentration uses the concentration obtained from automatic titration as the historical state at the sampling time. By analyzing the process consumption, discharge, and water replenishment data during the delay period, the concentration of the two acids at the replenishment decision time is reconstructed, reducing insufficient or excessive replenishment caused by detection lag.

Description

Technical Field

[0001] This invention relates to the field of automatic replenishment control of mixed acid solutions, and more specifically, to a precise replenishment control method that links the concentration of mixed acid solutions. Background Technology

[0002] In semiconductor and photovoltaic wet etching and cleaning processes, fluctuations in the concentrations of hydrofluoric acid and sulfuric acid in mixed acid solutions can alter reaction rates and product consistency. Existing technologies include CN104237332A, which discloses the determination of each acid concentration in a mixed acid solution using multiple titration equivalence points; US7214537B2, which discloses online monitoring of a multi-component chemical bath and replenishment of corresponding components; US11839860B2, which discloses maintaining target concentrations of multi-component chemicals based on mass balance; and WO2014082189A1, which discloses using a multivariable controller to handle the coupling relationship between multiple acid concentration measurements. However, these solutions primarily address component detection, final-state proportioning, or general coupling control, failing to address issues such as time lag between titration results and replenishment decisions, cross-dilution of one acid by replenishing another, and inconsistencies between commanded replenishment volumes and actual effective replenishment volumes caused by changes in pumps, valves, and pipelines. Directly replenishing two different solutions based on the concentration at the sampling time can easily lead to over-flushing, repeated compensation, or abnormal continuous replenishment. Therefore, it is necessary to propose a precise replenishment control method that can reconstruct the current dual acid concentration, constrain the intermediate replenishment trajectory, and calibrate the control parameters online based on the net dual acid response after replenishment. Summary of the Invention

[0003] The purpose of this invention is to provide a precise liquid replenishment control method that links the concentration of mixed acid solutions. This method solves the problems in existing automatic liquid replenishment schemes, such as titration results lagging behind the actual process conditions, mutual dilution of the two original solutions during replenishment, difficulty in online identification of the actual delivery capacity of the liquid replenishment execution channel, and the tendency to continuously add liquid under abnormal conditions.

[0004] This invention achieves the above objective through the following technical solution: a precise replenishment control method for mixed acid solution concentration linkage, applied to process tanks containing hydrofluoric acid and sulfuric acid in semiconductor or photovoltaic wet etching and cleaning processes, the method comprising:

[0005] The mixed acid solution in the process tank is circulated and sampled. When the sample enters the automatic potentiometric titration unit, a sampling time mark is generated, and process status data between the sampling time mark and the titration completion time mark is collected. Based on the hydrofluoric acid titration concentration and sulfuric acid titration concentration obtained by automatic potentiometric titration, and combined with the process status data, the mass of hydrofluoric acid consumed, the mass of sulfuric acid lost, and the change in tank liquid volume during the titration analysis are determined. The dual acid concentrations at the sampling time are reconstructed into the current concentrations of hydrofluoric acid and sulfuric acid at the replenishment decision time. A dual-acid cross-response matrix is ​​constructed, which includes the first principal response of hydrofluoric acid stock solution to hydrofluoric acid concentration, the first cross-dilution response of sulfuric acid concentration, the second cross-dilution response of sulfuric acid stock solution to hydrofluoric acid concentration, and the second principal response of sulfuric acid concentration. Based on the current concentration of hydrofluoric acid, the current concentration of sulfuric acid, their respective target concentration ranges, and the dual-acid cross-response matrix, the replenishment volume of hydrofluoric acid stock solution and the replenishment volume of sulfuric acid stock solution are jointly calculated. The intermediate concentration trajectories of the two acids formed when the two stock solutions are replenished sequentially are predicted. Trajectories that exceed the corresponding process limits are excluded, and the replenishment sequence corresponding to the trajectory with the smallest maximum normalized deviation among the remaining trajectories is determined as the target replenishment sequence. Perform pre-replenishment according to the target replenishment sequence, and lock the titration result before reaching the mixing determination condition; In the next titration cycle, the concentration changes caused by process reaction, drug carry-out, drainage and water replenishment before and after the pre-replenishment are deducted to obtain the net response amount of hydrofluoric acid and the net response amount of sulfuric acid, forming the dual acid response fingerprint of the corresponding replenishment channel. The effective delivery coefficient of the replenishment channel is determined based on the dual-acid response fingerprint, the dual-acid cross-response matrix is ​​updated, and the replenishment channel fault determination result is corrected or output based on the updated dual-acid cross-response matrix.

[0006] Furthermore, the cyclic sampling and automatic potentiometric titration include: The mixed acid solution in the process tank is continuously passed through the sampling point via an independent circulation pipeline, and the sampling time stamp is recorded when the sampling valve is turned on. Simultaneously record the effective liquid volume, chemical temperature, circulation flow rate, number of processed pieces, processing area, discharge volume, and water replenishment volume in the process tank; Add a known concentration of alkaline titrant to a quantitative mixed acid sample, continuously collect the cumulative amount of titrant added and the change in potential, and determine the titration concentrations of hydrofluoric acid and sulfuric acid respectively based on the corresponding titration endpoints of the titration curves. When the change in titration endpoint potential is lower than the effective lower limit determined by repeated titration of the standard mixed acid sample, or when the volume difference of titrant corresponding to adjacent titration endpoints exceeds the effective range of the standard mixed acid sample, the titration result is marked as invalid and a new sample is taken.

[0007] Furthermore, the dual acid concentration reconstruction includes: The difference between the titration completion time and the sampling time is used as the analytical delay time. Based on the processing area, liquid temperature, process formula, and hydrofluoric acid consumption parameters per unit processing area within the analysis delay time, the mass of hydrofluoric acid consumed is determined. The mass of sulfuric acid lost is determined based on the processing batches, liquid volume of the workpiece, and discharge volume within the analysis delay period. The current concentrations of hydrofluoric acid and sulfuric acid are obtained by subtracting the corresponding consumed mass from the mass of the single acid in the tank at the sampling time, and then dividing by the effective liquid volume of the process tank after water replenishment and drainage correction. The hydrofluoric acid consumption parameter per unit processing area is determined based on the ratio of the change in hydrofluoric acid mass to the processing area in a continuous normal production batch, and is updated after each effective correction and replenishment.

[0008] Furthermore, the initial parameters of the dual-acid cross-response matrix are determined based on the material balance relationship of the effective liquid volume of the process tank, the mass concentration of hydrofluoric acid stock solution, the mass concentration of sulfuric acid stock solution, the densities of the two stock solutions, and the concentrations of the dual acids before replenishment. The first and second main responses are positive, while the first and second cross-dilution responses are negative. The dimensions of each response are uniformly represented as the change in monoacid mass concentration per unit volume of the original solution.

[0009] Furthermore, the joint determination of the replenishment volume and the determination of the target replenishment sequence include: The final state constraint is that the concentrations of the two monoacids after replenishment are both within their respective target concentration ranges, and the process constraint is that the concentrations of the two monoacids after replenishment of the first stock solution do not exceed their respective process upper and lower limits. The replenishment amounts of the two stock solutions are then determined. Calculate the first trajectory of adding hydrofluoric acid stock solution first and then sulfuric acid stock solution, and the second trajectory of adding sulfuric acid stock solution first and then hydrofluoric acid stock solution. The normalized deviation is obtained by dividing the distance from the single acid concentration in each trajectory to the nearest boundary of the corresponding target concentration interval by the width of the target concentration interval. Trajectories that violate the process constraints are excluded, and the replenishment sequence corresponding to the trajectory with the smallest maximum normalized deviation among the remaining trajectories is determined as the target replenishment sequence.

[0010] Furthermore, the replenishment volume for each stock solution is divided into pre-replenishment volume and retention correction volume; When the sum of the repeatability error of automatic potentiometric titration and the flow rate error of the replenishment channel is no greater than 2%, the pre-replenishment volume is 90% of the corresponding original solution replenishment volume; When the sum of the errors is greater than 2% but not greater than 4%, the pre-replenishment volume is 80% of the corresponding original solution replenishment volume; When the sum of the errors is greater than 4%, the pre-replenishment volume is 70% of the corresponding original solution replenishment volume; After the pre-replenishment is completed, the basic circulation time is determined based on the ratio of the effective liquid volume in the process tank to the circulation flow rate, and no less than three basic circulation times are taken as the minimum mixing time. The titration result of the pre-replenishing solution is locked within the shortest mixing time. The lock is released when the shortest mixing time is reached and the rate of change of circulating flow rate and the rate of change of drug solution temperature are both below their respective stability thresholds within two consecutive basic cycles.

[0011] Furthermore, the formation of the dual-acid responsive fingerprint includes: Obtain the corresponding diacid concentration for the next effective titration after obtaining the pre-replenishment solution; Based on the processing area, liquid volume on the workpiece, drainage volume, and water replenishment volume between the two sampling time points, the change in dual acid concentration caused by non-liquid replenishment factors is calculated. Subtracting the changes in diacid concentrations caused by non-replenishment factors from the diacid concentration differences between the two consecutive tests, we obtain the net response of hydrofluoric acid and the net response of sulfuric acid. The dual-acid response fingerprint is formed by associating the replenishment medium identifier, the commanded replenishment volume, the replenishment pump runtime, the cumulative flow value, the net response amount of hydrofluoric acid, the net response amount of sulfuric acid, the temperature of the drug solution during replenishment, and the effective liquid volume of the process tank according to the same replenishment event.

[0012] Furthermore, the effective delivery coefficient is the ratio of the magnitude of the actual net response vector of the two acids to the magnitude of the theoretical response vector of the two acids. The theoretical response vector of the two acids is obtained by multiplying the response column vector of the corresponding replenishment channel in the two acid cross-response matrix with the commanded replenishment volume. When the actual net response direction of the two acids is consistent with the direction of the corresponding response column vector, and the effective delivery coefficient is between the 5th percentile and the 95th percentile of the historical normal replenishment event, the corresponding response column vector is updated using the ratio of the actual net response amount of the two acids to the commanded replenishment volume. The updated response column vector is used to determine the replenishment volume for the next replenishment cycle and to predict the intermediate concentration trajectory.

[0013] Furthermore, the fault determination of the replenishment channel is based on an effective response threshold, which is three times the standard deviation of the corresponding single acid concentration obtained from continuous measurements of the same standard mixed acid sample. The fault determination of the replenishment channel includes: When the actual response direction of the dual acid net is consistent with the theoretical response direction, and the effective delivery coefficient is lower than the lower limit of the normal range, it is determined that there is a delivery attenuation in the replenishment channel, and an inspection command is output indicating that the delivery capacity of the replenishment pump has decreased, the original liquid level is insufficient, there is air in the delivery pipeline, or the opening of the replenishment valve is insufficient. If the target single acid net response quantity does not exceed the corresponding effective response threshold, and the other single acid net response quantity exceeds the corresponding effective response threshold along the main response direction of the other replenishment channel, it is determined that the replenishment valve is cross-connected, the two raw liquid delivery pipelines are reversed, or the raw liquid container is connected incorrectly. If neither the net response of hydrofluoric acid nor the net response of sulfuric acid exceeds its respective effective response threshold, it is determined that the replenishment pump is running dry, the delivery pipeline is blocked, or the replenishment valve is not open. After the fault diagnosis result is generated, the corresponding replenishment pump is stopped and the corresponding replenishment valve is closed.

[0014] Furthermore, if the next effective titration result shows that the dual-acid response fingerprint is normal and the current concentration of hydrofluoric acid or sulfuric acid has not entered the corresponding target concentration range, the corrected replenishment volume is recalculated based on the updated dual-acid cross-response matrix. When the corrected replenishment amount is not greater than the corresponding retained corrected amount, perform corrected replenishment and re-mixing lock and automatic potentiometric titration; When the corrected replenishment volume is greater than the corresponding retained correction volume, the dual acid intermediate concentration trajectory prediction is re-executed. When the liquid leak detection value reaches the leak alarm threshold or the acid gas detection value reaches the gas alarm threshold, the hydrofluoric acid stock solution replenishment channel and the sulfuric acid stock solution replenishment channel are stopped, and the emergency ventilation is activated.

[0015] The beneficial effects of this invention are as follows: 1. This invention uses the concentration obtained by automatic titration as the historical state at the sampling time. By analyzing the process consumption, drainage and water replenishment data during the delay period, the concentration of the two acids at the time of replenishment decision is reconstructed, thereby reducing insufficient or excessive replenishment caused by detection lag.

[0016] 2. This invention describes the main response of two stock solutions to the target single acid and the cross-dilution response to another single acid simultaneously through a dual-acid cross-response matrix, so that the replenishment volume calculation can reflect the coupling relationship between the two replenishment actions and reduce repeated compensation caused by independent control.

[0017] 3. This invention predicts the intermediate concentration trajectory of two stock solutions under different replenishment sequences, and selects the replenishment sequence based on the upper and lower limits of the process and the normalized deviation, which can avoid any single acid from instantaneously exceeding the limit during the replenishment process.

[0018] 4. This invention adopts a phased control method of pre-filling, mixing and locking, and corrective replenishment. It prohibits repeated addition based on the same titration result before the drug solution has been fully circulated and mixed, thereby reducing the risk of over-flushing concentration.

[0019] 5. This invention forms a replenishment response fingerprint based on the net response of the two acids before and after replenishment, determines the effective delivery coefficient of the replenishment channel online, and updates the cross-response matrix of the two acids using the effective response parameters, which can compensate for the execution deviation caused by pump wear, changes in raw liquid batch and pipeline status.

[0020] 6. This invention can identify problems such as pump delivery attenuation, pump idling, pipeline blockage, valve cross-contamination, and incorrect raw material connection based on the direction and amplitude of the dual acid response, and stop the corresponding replenishment channel under abnormal conditions, thus avoiding masking equipment failures by continuously increasing the replenishment command.

[0021] 7. This invention can be interlocked with a dual-pipe delivery pipeline, a liquid leak detector, an acid gas detector, and an emergency ventilation device to improve the safety of the online replenishment process of highly corrosive mixed acid solution. Attached Figure Description

[0022] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a flowchart illustrating the overall process of the method of the present invention. Figure 2 This is a schematic diagram of the mixed acid drug solution concentration linkage precise replenishment control system of the present invention; Figure 3 This is a schematic diagram illustrating the time-shifted reconstruction principle of the dual-acid concentration of the present invention. Figure 4 This is a schematic diagram illustrating the calculation of dual-acid coupling replenishment and the selection of replenishment sequence in this invention; Figure 5 This is a schematic diagram of the liquid replenishment response fingerprint update and security interlock process of the present invention. Detailed Implementation

[0023] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0024] This invention is applied to semiconductor or photovoltaic wet etching and cleaning production lines, and is used to process mixed acid solutions containing at least hydrofluoric acid and sulfuric acid. For example... Figure 2 As shown, the replenishment equipment includes a circulating sampling unit, a fully automatic potentiometric titration unit, a PLC data processing and control unit, a hydrofluoric acid stock solution replenishment channel, a sulfuric acid stock solution replenishment channel, a double-tube delivery pipeline, a liquid leak detector, an acid gas detector, and an emergency exhaust system. The hydrofluoric acid and sulfuric acid stock solutions are stored in separate stock solution tanks and are respectively delivered to the process tank via replenishment pumps and replenishment valves. The sampling pipelines, titration tank, pump body flow parts, replenishment valves, and inner delivery pipelines that come into contact with the mixed acid solutions are made of PFA or PTFE corrosion-resistant materials.

[0025] In this embodiment, the concentration of the mixed acid solution is uniformly expressed as mass concentration, with the unit being g / L; the liquid volume is uniformly expressed as L; the mass is uniformly expressed as g; the flow rate is uniformly expressed as L / min; the time is uniformly expressed as min; and the temperature is uniformly expressed as... C; The unit for the dual-acid cross-response parameters is uniformly g / L2; The effective transport coefficient and normalized deviation are both dimensionless parameters.

[0026] Example 1: This embodiment provides a precise replenishment control method for mixed acid solution concentration linkage. The rated volume of the process tank is 1200 L, and the effective liquid volume during normal operation is 900 L to 1100 L. The rated flow rate of the solution circulation pipeline is 100 L / min. The hydrofluoric acid stock solution replenishment channel and the sulfuric acid stock solution replenishment channel are each equipped with a 25 L stock solution tank, and are respectively equipped with a corrosion-resistant replenishment pump, flow meter, and replenishment valve.

[0027] like Figure 1 As shown, the precise fluid replacement control method includes the following steps.

[0028] S1. Perform cyclic sampling and establish a sampling time scale. After the equipment starts, the circulating pump drives the mixed acid solution in the process tank to flow continuously along the independent circulating sampling pipeline, ensuring that the solution at the sampling point maintains circulation and exchange with the main solution in the process tank. When the sampling valve opens and sends the mixed acid solution sample into the fully automatic potentiometric titration unit, Record sampling time The sampling time will be used as the sampling time marker for this sample.

[0029] While generating the sampling time scale Synchronous acquisition of effective liquid volume in process tank Temperature of the medicine solution Circulation flow Number of processed pieces Processing area , displacement Water replenishment The process formula number is also recorded, and a unique correspondence is established between the above process status data and the sampling time point.

[0030] In this embodiment, 50 mL of mixed acid sample is taken from the circulating sampling pipeline each time, of which 0.50 mL is used for potentiometric titration, and the remaining sample is used for retesting and retention. The 0.50 mL sample to be tested is quantitatively diluted to 100 mL before titration.

[0031] The sample volume was determined through titrator range verification. During the equipment commissioning phase, titrations were performed using sample volumes of 0.25 mL, 0.50 mL, and 1.00 mL, respectively. The required titrant consumption was between 20% and 80% of the titrator's effective range, and the two titration endpoints were stably distinguishable. After repeated testing, the endpoint discrimination and repeatability corresponding to the 0.50 mL sample met the control requirements; therefore, this volume was determined as the sample volume for formal operation.

[0032] The effective liquid volume in the process tank is determined by the output value of the level sensor and the tank volume calibration curve. The tank volume calibration curve is established during the equipment installation phase using a staged water injection method. The level sensor output value is recorded every 50 L of water added. During operation, the current effective liquid volume is obtained by linear interpolation between two adjacent calibration points.

[0033] The discharge volume and replenishment volume are determined by the cumulative values ​​of the corresponding flow meters. Before operation, the flow meters are calibrated using a weighing method, with a continuous calibration time of no less than 5 minutes. When the relative error between the measured cumulative volume and the weighed converted volume of the flow meter exceeds 1%, the PLC will prevent entry into automatic replenishment mode and output a flow meter recalibration prompt.

[0034] S2. Perform fully automated potentiometric titration and determine the validity of the titration results. The fully automated potentiometric titration unit uses a 0.1 mol / L sodium hydroxide standard solution as the titrant. During the titration process, the titration device adds the titrant to the diluted mixed acid sample at a minimum addition resolution of 0.01 mL, and continuously collects the cumulative volume of titrant added, electrode potential, and sample temperature.

[0035] The PLC determines the corresponding titration endpoint based on the local extrema of the potential change rate in the titration curve, and calculates the hydrofluoric acid and sulfuric acid titration concentrations at the sampling time based on the titrant consumption volume corresponding to each titration endpoint. When completing the dual-acid concentration conversion, the PLC records the titration completion time t1 and uses it as the titration completion time marker.

[0036] In this embodiment, the total time from generating the sampling timescale to completing the dual acid concentration conversion is controlled within 20 minutes.

[0037] The validity of the titration results was determined through tests using standard mixed acid samples. During the equipment commissioning phase, low-concentration, intermediate-concentration, and high-concentration standard mixed acid samples were prepared, and each standard mixed acid sample was titrated 20 times consecutively. The 5th percentile of the rate of change of the endpoint potential in the qualified titration results was determined as the lower limit of endpoint identification, and the 5th percentile to the 95th percentile of the volume difference of the titrant corresponding to two adjacent titration endpoints was determined as the effective volume difference range.

[0038] When the rate of change of potential at the titration endpoint is lower than the endpoint recognition limit, or when the volume difference of titrant corresponding to two adjacent titration endpoints exceeds the effective volume difference range, the PLC will mark the titration result as invalid, prohibit the result from triggering liquid replenishment, and control the cyclic sampling unit to resample.

[0039] Titration repeatability error is expressed as the relative standard deviation of the concentration results obtained from 10 consecutive measurements of the same standard mixed acid sample. When the relative standard deviation of hydrofluoric acid concentration or sulfuric acid concentration is greater than 2%, the PLC outputs an electrode calibration prompt and switches the equipment to a detection-only, non-automatic liquid replenishment operation mode.

[0040] S3. Time-shift reconstruction of titration concentration. like Figure 3 As shown, the concentration obtained by fully automated potentiometric titration corresponds to the sampling time. The decision to replenish fluid occurs at the moment the titration is completed. Therefore, in to Process reactions, liquid carryover from the workpiece, liquid drainage, and water replenishment that occur during the process will cause changes in the actual concentration in the process tank. Therefore, the PLC reconstructs the titration concentration at the sampling time to the current concentration at the time of the replenishment decision based on the process status data during the analysis.

[0041] For any single acid component in hydrofluoric acid or sulfuric acid, its current reconstitution concentration is determined according to equation (1):

[0042] In the formula, This indicates hydrofluoric acid or sulfuric acid; Indicates monoacid components The reconstructed concentration at the time of fluid replacement decision, in units of ; Indicates monoacid components The titration concentration at the time of sampling, in units of... ; The effective liquid volume in the process tank at the sampling time is expressed in units of... ; This indicates the volume of fluid discharged during the analysis period, in units of... ; This indicates the amount of water replenished during the analysis period, in units of... ; Indicates the single acid component during the analysis period The mass loss due to process reactions and liquid carryover in the workpiece is expressed in units of... .

[0043] The numerator of equation (1) represents the remaining mass of the corresponding single acid in the tank at the time of replenishment decision, in units of 1. The denominator represents the effective liquid volume in the process tank at the moment of liquid replenishment decision, in units of... ,therefore The dimensions are .

[0044] The hydrofluoric acid mass loss is determined based on the actual processing area, solution temperature, process formula, and hydrofluoric acid consumption parameters per unit processing area. During initial equipment commissioning, at least 30 normal production batches without alarms and with complete replenishment records are selected. The hydrofluoric acid mass reduction between two consecutive effective titrations is calculated. After deducting the mass changes caused by simultaneous replenishment and drainage, the result is divided by the corresponding processing area to obtain the hydrofluoric acid consumption parameters per unit processing area for each batch. The PLC takes the median of the results from the 30 batches as the initial hydrofluoric acid consumption parameters.

[0045] The sulfuric acid mass loss is determined based on the number of processed pieces, the volume of liquid carried by a single workpiece, and the drainage status. The volume of liquid carried by a single workpiece is obtained by dividing the difference in weight of the workpiece before and after entering the process tank by the density of the mixed acid solution. For each product specification, 20 workpieces are continuously measured, and the median of the 20 measurements is taken as the volume of liquid carried by a single workpiece for the corresponding product specification.

[0046] During equipment operation, the PLC saves hydrofluoric acid consumption parameters and sulfuric acid loss parameters for the most recent 30 valid production batches. After each valid replenishment cycle, the earliest data set is deleted, and the current cycle's data is added; the median is then used as the parameter for the next cycle. This update method does not use manually set weighting coefficients, thus reducing the impact of abnormal production batches on the concentration reconstruction results.

[0047] When no workpiece processing is performed on the production equipment between the sampling time point and the titration completion time point, the mass loss of hydrofluoric acid generated by the process reaction is set to zero; the mass loss of sulfuric acid is determined only based on the recorded liquid content of the workpiece; the discharge volume and water replenishment volume are still corrected according to the cumulative value of the flow meter.

[0048] S4. Construct the dual-acid cross-response matrix When hydrofluoric acid stock solution is added, the hydrofluoric acid concentration increases, and at the same time, due to the increase in the total liquid volume of the process tank, the sulfuric acid concentration is diluted; when sulfuric acid stock solution is added, the sulfuric acid concentration increases, and at the same time, the hydrofluoric acid concentration is diluted. The PLC establishes a dual-acid cross-response matrix to simultaneously describe the main response and cross-dilution response of the two stock solutions to the two single acid concentrations, as shown in equation (2):

[0049] In the formula, This indicates the change in hydrofluoric acid concentration caused by the replenishment of the solution, in units of... ; This indicates the change in sulfuric acid concentration caused by the replenishment of the solution, in units of... ; This indicates the volume of hydrofluoric acid stock solution replenished, in units of... ; This indicates the volume of sulfuric acid stock solution replenished, in units of... .

[0050] This represents the first primary response produced per unit volume of hydrofluoric acid stock solution to the concentration of hydrofluoric acid. This represents the first cross-dilution response per unit volume of hydrofluoric acid stock solution to sulfuric acid concentration; This represents the second cross-dilution response per unit volume of sulfuric acid stock solution to hydrofluoric acid concentration; This represents the second primary response produced per unit volume of sulfuric acid stock solution in response to sulfuric acid concentration. , , and All units are .

[0051] First primary response parameters Second principal response parameters The first cross-dilution response parameter is positive. Second cross-dilution response parameters It is a negative value.

[0052] The initial value of the dual-acid cross-response matrix is ​​determined based on the effective liquid volume of the process tank, the actual mass concentration of the hydrofluoric acid stock solution, the actual mass concentration of the sulfuric acid stock solution, and the concentrations of the dual acids before replenishment, according to the material balance relationship.

[0053] The actual mass concentration of the stock solution is not directly taken from the nominal value on the stock solution container. After each batch of stock solution is changed, the hydrofluoric acid stock solution and the sulfuric acid stock solution are subjected to three density tests and three standard titrations respectively. The median of the three concentration test results is taken as the effective mass concentration of the stock solution of that batch.

[0054] After the initial matrix is ​​established, three diagnostic micro-replenishment tests are performed on each of the two replenishment channels. Only one replenishment channel is activated for each diagnostic replenishment test, and the diagnostic replenishment volume must not exceed 0.1% of the current effective liquid volume in the process tank. Furthermore, the change in concentration of any single acid calculated theoretically must not exceed 20% of the width of the corresponding target concentration range. When the 0.1% volume limit and the 20% concentration change limit are inconsistent, the minimum value of the replenishment volume corresponding to the two constraints is used.

[0055] After each diagnostic micro-volume rehydration was completed and the mixing conditions were met, a new titration was performed. The actual response parameters of the corresponding rehydration channel were obtained by dividing the net change in the concentration of the two acids (after deducting normal process consumption) by the actual rehydration volume. The median of the response parameters obtained from three diagnostic rehydration tests was used to correct the initial values ​​of the matrix.

[0056] S5. Calculate the replenishment volume of both stock solutions. like Figure 4As shown, the PLC compares the reconstituted hydrofluoric acid concentration with the target concentration range of hydrofluoric acid, and compares the reconstituted sulfuric acid concentration with the target concentration range of sulfuric acid. When the reconstituted concentration of at least one single acid is lower than the lower limit of the corresponding target concentration range, the PLC simultaneously calculates the replenishment volume of hydrofluoric acid stock solution and the replenishment volume of sulfuric acid stock solution according to formula (2).

[0057] The replenishment volume calculation must meet the following conditions: the predicted concentration of hydrofluoric acid after replenishment is within the target concentration range of hydrofluoric acid; the predicted concentration of sulfuric acid after replenishment is within the target concentration range of sulfuric acid; the cross-dilution caused by replenishing hydrofluoric acid stock solution must not cause the sulfuric acid concentration to fall below the lower limit of the sulfuric acid process; the cross-dilution caused by replenishing sulfuric acid stock solution must not cause the hydrofluoric acid concentration to fall below the lower limit of the hydrofluoric acid process; the predicted concentrations of hydrofluoric acid and sulfuric acid formed in any replenishment stage must not exceed the corresponding upper limit of the process; the replenishment volume of any stock solution in a single replenishment cycle must not exceed 1% of the current effective liquid volume of the process tank.

[0058] The target concentration range, upper and lower limits of the process are determined based on the product process validation results. During process validation, starting from the target concentration of the process formulation, the concentration of the single acid is gradually changed upwards and downwards, with each level of concentration change set at 25% of the width of the target concentration range. Surface quality testing is performed on the product treated at each concentration level, and the concentration corresponding to the level before the product quality indicators begin to exceed the control limits is determined as the upper or lower limit of the process.

[0059] The initial upper limit for a single replenishment volume is set to 1% of the current effective liquid volume in the process tank. During equipment commissioning, mixing tests are conducted using single replenishment ratios of 0.5%, 0.75%, and 1.0%. If a 1.0% replenishment volume cannot achieve uniform mixing within three basic cycles, or if it causes any local concentration to exceed the process limit, the replenishment ratio that first meets the mixing and concentration safety requirements in the order of 1.0%, 0.75%, and 0.5% is selected as the upper limit for a single replenishment volume.

[0060] When there are multiple sets of replenishment volumes that meet the above constraints, the PLC selects the set with the smallest sum of hydrofluoric acid stock replenishment volume and sulfuric acid stock replenishment volume as the replenishment volume for this cycle, in order to reduce the change in the total liquid volume of the process tank and the consumption of stock solution.

[0061] S6. Predict the intermediate concentration trajectory of the two acids and determine the target replenishment sequence. The PLC predicts the intermediate concentration trajectories of the first dual acid formed by first adding hydrofluoric acid stock solution and then adding sulfuric acid stock solution, as well as the intermediate concentration trajectories of the second dual acid formed by first adding sulfuric acid stock solution and then adding hydrofluoric acid stock solution.

[0062] For each replenishment sequence, the PLC sequentially calculates the intermediate concentrations of hydrofluoric acid and sulfuric acid after the first stock solution is added, as well as the final predicted concentrations of hydrofluoric acid and sulfuric acid after the second stock solution is added.

[0063] If any intermediate concentration is lower than the corresponding lower process limit or higher than the corresponding upper process limit, the replenishment sequence is excluded. For the remaining replenishment sequences, the maximum normalized deviation is calculated according to equation (2):

[0064] In the formula, Indicates the first The maximum normalized deviation of the fluid replacement sequence is a dimensionless parameter. Indicates the order of candidate fluid replacements; This indicates hydrofluoric acid or sulfuric acid; This indicates the intermediate stage after the first stock solution is added, or the final stage after both stock solutions are added. Indicates the first Components in the order of fluid replenishment In the stage The predicted concentration, in units of ; and Each represents a component The target concentration lower limit and target concentration upper limit, in units of .

[0065] When the predicted concentration is within the target concentration range, the distance function Set to zero; when the predicted concentration is below the lower limit of the target concentration, the distance function... The difference between the lower limit of the target concentration and the predicted concentration is taken; when the predicted concentration is higher than the upper limit of the target concentration, the distance function is used. The difference between the predicted concentration and the upper limit of the target concentration is taken. Distance function. The unit is Target concentration range width The unit is also ,therefore It is a dimensionless parameter.

[0066] The PLC determines the replenishment sequence with the smallest maximum normalized deviation among the two candidate replenishment sequences as the target replenishment sequence. When the difference between the maximum normalized deviations of the two replenishment sequences is less than the deviation judgment threshold, the replenishment sequence with the smaller replenishment volume in the first stage is selected.

[0067] The deviation threshold is determined based on the titration repeatability error. The standard deviations of the titration repeatability for hydrofluoric acid and sulfuric acid are divided by the width of their respective target concentration ranges to obtain two normalized repeatability errors. The larger of these two values ​​is taken as the deviation threshold. In this embodiment, the deviation threshold obtained during equipment debugging is 0.05.

[0068] S7. Perform pre-filling and implement mixing lock. The PLC divides the calculated replenishment volume for each stock solution into a pre-replenishment volume and a retention correction volume. The pre-replenishment ratio is determined based on the sum of the titration repeatability error and the corresponding replenishment channel flow rate error.

[0069] When the sum of errors is no greater than 2%, the pre-replenishment ratio is set to 90%; when the sum of errors is greater than 2% but no greater than 4%, the pre-replenishment ratio is set to 80%; when the sum of errors is greater than 4%, the pre-replenishment ratio is set to 70%.

[0070] The above grading rules were determined through equipment verification. During the equipment commissioning phase, 10 replenishment cycles were performed at pre-replenishment ratios of 70%, 80%, and 90%, respectively. The occurrence of concentration overshoot and the number of corrections required to achieve the target concentration adjustment were recorded. Under the condition of no concentration overshoot, the highest pre-replenishment ratio that resulted in the fewest average corrections was selected.

[0071] The PLC starts the corresponding replenishment pumps and valves according to the target replenishment sequence, and performs pre-replenishment through the double-tube delivery pipeline. After the pre-replenishment is completed, the titration result that triggered this replenishment is set to a locked state. Before the mixed acid solution reaches the mixing condition, it is prohibited to trigger replenishment again based on the same titration result.

[0072] The basic circulation time is determined by dividing the current effective liquid volume in the process tank by the circulation flow rate. The minimum mixing time is set to three basic circulation times.

[0073] The three basic cycle times were determined through tracer experiments. During the equipment commissioning phase, tracer liquid that does not participate in the current process reaction and can be detected by the auxiliary sensor was added from the replenishment point, and the detection values ​​at the sampling points were continuously recorded. When the difference in tracer signals within three consecutive basic cycle times does not exceed the repeatability error of the auxiliary sensor, the three basic cycle times are considered to meet the mixing requirements.

[0074] After reaching the shortest mixing time, the PLC further determines the relative change rate of the circulating flow rate and the change rate of the liquid temperature. The threshold for the relative change rate of the circulating flow rate is set to twice the absolute value of the flowmeter calibration error. In this embodiment, the flowmeter calibration error is 0.5%, therefore the threshold for the relative change rate of the circulating flow rate is set to 1%.

[0075] The threshold for the rate of temperature change of the drug solution is determined based on the resolution of the temperature sensor and the allowable rate of temperature change in the process. In this embodiment, the resolution of the temperature sensor is [missing information]. The process allows for a temperature change rate of 100%. Take the allowable temperature change rate of the process. ,Right now , which serves as the threshold for the rate of change of the liquid temperature.

[0076] When the shortest mixing time has been reached, and the relative rate of change of circulating flow rate within two consecutive basic cycles is no greater than [value missing], The rate of change in the temperature of the liquid medicine should not exceed [a certain value]. hour, Release the titration result lockout, allowing the next cycle of sampling and automatic potentiometric titration to be performed.

[0077] S8, Generate dual-acid response fingerprint After the pre-replenishment is completed and the mixing conditions are met, the automatic potentiometric titration unit re-acquires the mixed acid solution sample to obtain the measured concentrations of hydrofluoric acid and sulfuric acid after the pre-replenishment.

[0078] The PLC calculates the changes in the concentration of the two acids caused by non-replenishment factors based on the processing area, number of processed pieces, liquid volume of the workpiece, drainage volume, and water replenishment volume between the two sampling time points. It then subtracts the influence of non-replenishment factors from the concentration difference between the two measured times to obtain the net response of hydrofluoric acid and the net response of sulfuric acid.

[0079] The PLC associates the replenishment medium identifier, the commanded replenishment volume, the replenishment pump running time, the flow meter cumulative value, the net response amount of hydrofluoric acid, the net response amount of sulfuric acid, the temperature of the drug solution during replenishment, the effective liquid volume of the process tank, and the actual mixing time into the same replenishment event, forming a dual-acid response fingerprint for that replenishment event.

[0080] The normal response direction for the hydrofluoric acid stock solution replenishment channel is that the net response amount of hydrofluoric acid is positive and the net response amount of sulfuric acid is negative; the normal response direction for the sulfuric acid stock solution replenishment channel is that the net response amount of sulfuric acid is positive and the net response amount of hydrofluoric acid is negative.

[0081] The effective response threshold for a single acid is set to three times the standard deviation of the titration repeatability for that single acid. The titration repeatability standard deviation is calculated from the results of 10 consecutive titrations of the same standard mixed acid sample and is redefined after each electrode calibration. Using three times the standard deviation as the effective response threshold can distinguish between random fluctuations in titration and the actual replenishment response.

[0082] When only one replenishment channel performs replenishment within a replenishment cycle, the response fingerprint of the corresponding replenishment channel is directly determined based on the net response of the two acids. When both replenishment channels perform replenishment, the total net response is decomposed into channels based on the commanded replenishment volumes of the two channels and the cross-response matrix of the two acids. When the absolute value of the matrix determinant is lower than the minimum identifiable value determined during the equipment commissioning phase, the parameters of individual channels are not updated; only the overall replenishment response is judged to be normal.

[0083] The minimum distinguishable value was determined through a diagnostic micro-infusion test. The diagnostic infusion volumes of the two stock solutions were varied, the determinant of the resulting matrix was calculated, and the absolute value of the smallest determinant that allowed the responses of the two infusion channels to be stably distinguishable was taken as the minimum distinguishable value.

[0084] S9. Determine the effective transport coefficient and update the dual-acid cross-response matrix. For any replenishment channel, its effective delivery coefficient is determined according to equation (4):

[0085] In the formula, Indicates the first The effective delivery coefficient of each fluid replenishment channel is a dimensionless parameter. This represents the actual net dual-acid response vector for the corresponding replenishment channel, with elements in units of 1. ; Represents the first acid in the dual-acid cross-response matrix. The response column vector corresponding to each fluid replenishment channel, with elements in units of ; Indicates the first The commanded replenishment volume for each replenishment channel, in units of... ;symbol This represents the magnitude of a vector.

[0086] In the denominator of equation (4), the unit of the response column vector is... Multiply by the volume of the replenishing solution The following unit is The unit is consistent with that of the molecule, therefore the effective transport coefficient is... It is a dimensionless parameter.

[0087] After the equipment completes its initial commissioning, collect at least [amount] from each of the two replenishment channels. A normal replenishment event should simultaneously meet the following requirements: correct response direction, no leak alarm triggered, no acid gas alarm triggered, valid titration results, and mass change after replenishment meeting material balance requirements.

[0088] For each rehydration channel, the effective delivery coefficients of 30 normal rehydration events are arranged in ascending order of value. The 5th percentile is used as the lower limit of the normal interval, and the 95th percentile is used as the upper limit of the normal interval. Separate normal intervals are established for the two rehydration channels, and they do not share the same threshold.

[0089] When the actual net response direction of the two acids is consistent with the theoretical response direction, and the effective delivery coefficient is within the normal range, the net response vector of the two acids is divided by the actual replenishment volume to obtain a set of effective response parameters. The PLC saves the most recent 5 sets of effective response parameters for the corresponding replenishment channel, takes the median of each response component in the 5 sets of data, and updates the corresponding response column vector in the two acid cross-response matrix.

[0090] This update method does not set manual weights and does not use a weighted summation of old and new parameters, which can avoid historical data from affecting current fluid resuscitation control with fixed weights for a long time.

[0091] When the actual response direction of the dual acid solution is consistent with the theoretical response direction, but the effective delivery coefficient is lower than the lower limit of the normal range, the PLC determines that there is a delivery attenuation in the corresponding replenishment channel and outputs inspection prompts for wear of the replenishment pump, insufficient raw liquid level, air in the delivery pipeline, or insufficient opening of the replenishment valve.

[0092] When the net response of the target single acid does not exceed the corresponding effective response threshold, while the other single acid changes along the main response direction of another replenishment channel and exceeds its effective response threshold, the PLC determines that there is cross-contamination of the replenishment valve, reversed connection of the two raw liquid delivery pipelines, or incorrect connection of the raw liquid tank.

[0093] When the net response of hydrofluoric acid and the net response of sulfuric acid do not exceed the corresponding effective response threshold, the PLC determines that the replenishment pump is running dry, the delivery pipeline is blocked, or the replenishment valve is not open.

[0094] S10, Perform corrective fluid replenishment and safety interlock. like Figure 5 As shown, when the dual-acid response fingerprint is within the corresponding normal range, but the next effective titration result shows that the hydrofluoric acid reconstruction concentration or sulfuric acid reconstruction concentration has not entered the corresponding target concentration range, the PLC recalculates the correct replenishment volume based on the updated dual-acid cross-response matrix.

[0095] When the corrected replenishment amount is not greater than the corresponding retained corrected amount, the PLC performs the corrected replenishment according to the updated target replenishment sequence. After the corrected replenishment is completed, the mixing lock, cyclic sampling, and automatic potentiometric titration are re-executed.

[0096] When the corrected replenishment amount is greater than the corresponding retained correction amount, the PLC does not directly execute the replenishment. Instead, it recalculates the combined replenishment amount of the two acids and predicts the intermediate concentration trajectory of the two acids to prevent the original replenishment plan from being used when the process status has changed.

[0097] When a fault is detected in the replenishment channel, the PLC stops the corresponding replenishment pump and closes the corresponding replenishment valve, and prohibits the elimination of the current concentration deviation by increasing the replenishment command.

[0098] The liquid leak detection threshold is determined based on the baseline test of the leak sensor. After the equipment is installed, the sensor output value is continuously collected for 30 minutes under no liquid leak conditions. The baseline mean plus 3 times the baseline standard deviation is taken as the leak warning threshold. Then, the wetting response is calibrated using a standard volume of liquid droplet. The lowest wetting response value that can be stably identified for 3 consecutive times is taken as the leak interlock threshold.

[0099] When the liquid leak detection value reaches the warning threshold but is below the interlock threshold, the PLC outputs a leak warning and prohibits the initiation of new liquid replenishment tasks; when the liquid leak detection value reaches the interlock threshold, the PLC immediately stops the hydrofluoric acid stock solution replenishment channel and the sulfuric acid stock solution replenishment channel, and closes the two replenishment valves.

[0100] The acid gas alarm threshold is determined based on the applicable occupational exposure limits for the location where the equipment is used and the alarm values ​​specified by the acid gas sensor manufacturer. The first-level alarm threshold is the minimum of 50% of the applicable occupational exposure limit and the sensor manufacturer's low alarm value; the liquid replenishment interlock threshold is the minimum of the applicable occupational exposure limit and the sensor manufacturer's high alarm value.

[0101] When the acid gas detection value reaches the first-level alarm threshold, the PLC starts emergency ventilation and prohibits the start of new liquid replenishment tasks; when the acid gas detection value reaches the liquid replenishment interlock threshold, the PLC stops the two liquid replenishment channels, closes the corresponding liquid replenishment valves, and continues to start emergency ventilation.

[0102] Example 2: This embodiment uses effective liquid volume as... Taking a wet cleaning process tank as an example, the above control process will be explained in detail.

[0103] Based on the process validation results for the corresponding product, the target concentration range for hydrofluoric acid is set as follows: to The process limit for hydrofluoric acid is set as follows: to The target concentration range for sulfuric acid is set as follows: to The sulfuric acid process limit is set as follows: to .

[0104] After density testing and standard titration, the effective mass concentration of this batch of hydrofluoric acid stock solution was determined to be: The effective mass concentration of the sulfuric acid stock solution is: .

[0105] In a certain sampling cycle, the effective liquid volume of the process tank at the sampling time for , Discharge during analysis for Water replenishment for The fully automated potentiometric titration unit obtained the hydrofluoric acid titration concentration at the sampling time as follows: The sulfuric acid titration concentration is .

[0106] According to recent The median of the effective production batches is used to determine the... The mass loss of internal hydrofluoric acid is The mass loss of sulfuric acid is .

[0107] Substituting the above parameters into equation (1), the hydrofluoric acid reconstitution concentration at the time of replenishment decision is approximately The sulfuric acid reconstitution concentration is approximately .

[0108] After material balance calculations and diagnostic micro-liquid replenishment correction, the first principal response parameter in the dual-acid cross-response matrix for this period is... for Second cross-dilution response parameters for First cross-dilution response parameters for Second main response parameter for .

[0109] Using the midpoint of the target concentration range of hydrofluoric acid The midpoint of the target concentration range for sulfuric acid As the control target for this cycle, substituting the current concentration difference and the dual-acid cross-response matrix into equation (2), the combined amount of hydrofluoric acid stock solution replenishment is approximately... The replenishment volume of the sulfuric acid stock solution is approximately The replenishment volume of both raw solutions was lower than the effective liquid volume of the process tank. This satisfies the single-time liquid replenishment volume constraint.

[0110] When replenishing the hydrofluoric acid stock solution first, the intermediate concentration of hydrofluoric acid in the first stage is approximately The intermediate concentration of sulfuric acid is approximately When sulfuric acid stock solution is added first, the intermediate concentration of hydrofluoric acid in the first stage is approximately... The intermediate concentration of sulfuric acid is approximately Neither of the two replenishment sequences caused the concentration of the single acid to exceed the corresponding process limit.

[0111] Substituting the predicted concentrations of the two replenishment sequences into equation (3), the maximum normalized deviation of the trajectory corresponding to replenishing hydrofluoric acid stock solution first is approximately The maximum normalized deviation of the trajectory corresponding to the initial addition of sulfuric acid stock solution is approximately .therefore, The target replenishment sequence is to first add hydrofluoric acid stock solution, then add sulfuric acid stock solution.

[0112] The repeatability error of this periodic automatic potentiometric titration is The flow rate error of the replenishment channel is The sum of the two is , in a position greater than and not greater than The range, therefore the pre-replenishment ratio is set to... .

[0113] The amount of hydrofluoric acid stock solution pre-replenished is approximately The remaining correction amount is approximately The pre-replenishment volume of sulfuric acid stock solution is approximately... The remaining correction amount is approximately .

[0114] First, activate the hydrofluoric acid stock solution replenishment channel to replenish... Hydrofluoric acid stock solution, then restart the sulfuric acid stock solution replenishment channel to supplement. Sulfuric acid stock solution. After the pre-replenishment is completed, the titration result that triggered this replenishment is locked.

[0115] The circulating flow for this period is The effective liquid volume of the process tank is Therefore, the basic loop time is The shortest mixing time is Complete pre-filling. back, Continue monitoring the circulation flow rate and solution temperature over two consecutive baseline cycles. When the relative rate of change in circulation flow rate is no greater than [value missing], [further monitoring is needed]. The rate of change in the temperature of the liquid medicine should not exceed [a certain value]. At that time, the titration result lockout is released and sampling and titration are performed again.

[0116] According to equation (2), the theoretical change in hydrofluoric acid concentration in this pre-replenishment solution is an increase of The theoretical change in sulfuric acid concentration is an increase. .

[0117] After the next titration, the concentration changes caused by concurrent process reactions, liquid carryover in the workpiece, liquid draining, and water replenishment are deducted to obtain the actual net hydrofluoric acid response as an increase. The actual net response of sulfuric acid was an increase. .

[0118] Substituting the actual net response of the two acids, the cross-response matrix of the two acids, and the actual replenishment volume into equation (4), the effective delivery coefficient of this replenishment event is calculated to be approximately .

[0119] The nearest corresponding fluid infusion channel The effective delivery coefficient for a normal fluid resuscitation event. percentiles , No. percentiles Therefore, the effective transport coefficient is within the normal range. Add the actual response parameters to the valid parameter sequence and take the nearest one. The median of the effective response parameters of the group is used to update the dual-acid cross-response matrix.

[0120] If the reconstituted hydrofluoric acid concentration is still lower than [the required level] after retesting Then, the hydrofluoric acid correction replenishment amount is calculated based on the updated dual-acid cross-response matrix. When the hydrofluoric acid correction replenishment amount is not greater than... When the hydrofluoric acid correction fluid volume is greater than 100%, perform corrective replenishment; when the corrective replenishment volume is greater than 100%, perform corrective replenishment. At that time, the combined calculation of the replenishment volume of the two original solutions and the prediction of the replenishment sequence should be performed again.

[0121] If the effective transport coefficient is lower than However, the actual direction of the dual acid response is still consistent with the theoretical direction. Stop the corresponding replenishment channel and output inspection prompts indicating that the replenishment pump delivery is weakening, the original liquid level is insufficient, there is air in the delivery pipeline, or the replenishment valve opening is insufficient.

[0122] If the net response of hydrofluoric acid does not exceed the corresponding effective response threshold after replenishment, while the net response of sulfuric acid increases in the main response direction, then the output original liquid tank is incorrectly connected, the delivery pipeline is reversed, or the replenishment valve is cross-connected.

[0123] If neither the net response of hydrofluoric acid nor the net response of sulfuric acid exceeds its respective effective response threshold, an alert will be issued indicating that the output replenishment pump is running dry, the delivery pipeline is blocked, or the replenishment valve is not open, and the corresponding replenishment valve will be closed.

[0124] Through the above implementation method, the historical titration concentration at the sampling time is reconstructed into the current concentration at the replenishment decision time. At the same time, the replenishment volume and replenishment order are determined based on the main response and cross-dilution response of the two stock solutions to the dual acid concentrations. The replenishment channel and dual acid cross-response matrix are calibrated online using the actual net dual acid response after replenishment. This forms a closed-loop control process of cyclic sampling, automatic titration, concentration time-shift reconstruction, dual acid coupling calculation, sequential pre-replenishment, mixing and locking, response fingerprint generation, matrix update and replenishment correction.

[0125] The above embodiments provide a detailed description of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A precise fluid replenishment control method based on the concentration linkage of mixed acid solutions, characterized in that, A process bath containing hydrofluoric acid and sulfuric acid, used in wet etching and cleaning processes for semiconductors or photovoltaics, the method comprising: The mixed acid solution in the process tank is circulated and sampled. When the sample enters the automatic potentiometric titration unit, a sampling time mark is generated, and process status data between the sampling time mark and the titration completion time mark is collected. Based on the hydrofluoric acid titration concentration and sulfuric acid titration concentration obtained by automatic potentiometric titration, and combined with the process status data, the mass of hydrofluoric acid consumed, the mass of sulfuric acid lost, and the change in tank liquid volume during the titration analysis are determined. The dual acid concentrations at the sampling time are reconstructed into the current concentrations of hydrofluoric acid and sulfuric acid at the replenishment decision time. A dual-acid cross-response matrix is ​​constructed, which includes the first principal response of hydrofluoric acid stock solution to hydrofluoric acid concentration, the first cross-dilution response to sulfuric acid concentration, the second cross-dilution response of sulfuric acid stock solution to hydrofluoric acid concentration, and the second principal response to sulfuric acid concentration. Based on the current concentration of hydrofluoric acid, the current concentration of sulfuric acid, their respective target concentration ranges, and the dual-acid cross-response matrix, the replenishment volume of hydrofluoric acid stock solution and the replenishment volume of sulfuric acid stock solution are jointly calculated. The intermediate concentration trajectories of the two acids formed when the two stock solutions are replenished sequentially are predicted. Trajectories that exceed the corresponding process limits are excluded, and the replenishment sequence corresponding to the trajectory with the smallest maximum normalized deviation among the remaining trajectories is determined as the target replenishment sequence. Perform pre-replenishment according to the target replenishment sequence, and lock the titration result before reaching the mixing determination condition; In the next titration cycle, the concentration changes caused by process reaction, drug carry-out, drainage and water replenishment before and after the pre-replenishment are deducted to obtain the net response amount of hydrofluoric acid and the net response amount of sulfuric acid, forming the dual acid response fingerprint of the corresponding replenishment channel. The effective delivery coefficient of the replenishment channel is determined based on the dual-acid response fingerprint, the dual-acid cross-response matrix is ​​updated, and the replenishment channel fault determination result is corrected or output based on the updated dual-acid cross-response matrix.

2. The precise fluid replenishment control method for mixed acid drug solution concentration linkage according to claim 1, characterized in that, The cyclic sampling and automatic potentiometric titration include: The mixed acid solution in the process tank is continuously passed through the sampling point via an independent circulation pipeline, and the sampling time stamp is recorded when the sampling valve is turned on. Simultaneously record the effective liquid volume, chemical temperature, circulation flow rate, number of processed pieces, processing area, discharge volume, and water replenishment volume in the process tank; Add a known concentration of alkaline titrant to a quantitative mixed acid sample, continuously collect the cumulative amount of titrant added and the change in potential, and determine the titration concentrations of hydrofluoric acid and sulfuric acid respectively based on the corresponding titration endpoints of the titration curves. When the change in titration endpoint potential is lower than the effective lower limit determined by repeated titration of the standard mixed acid sample, or when the volume difference of titrant corresponding to adjacent titration endpoints exceeds the effective range of the standard mixed acid sample, the titration result is marked as invalid and a new sample is taken.

3. The precise fluid replenishment control method for mixed acid solution concentration linkage according to claim 2, characterized in that, The dual acid concentration reconstruction includes: The difference between the titration completion time and the sampling time is used as the analytical delay time. Based on the processing area, liquid temperature, process formula, and hydrofluoric acid consumption parameters per unit processing area within the analysis delay time, the mass of hydrofluoric acid consumed is determined. The mass of sulfuric acid lost is determined based on the processing batches, liquid volume of the workpiece, and discharge volume within the analysis delay period. The current concentrations of hydrofluoric acid and sulfuric acid are obtained by subtracting the corresponding consumed mass from the mass of the single acid in the tank at the sampling time, and then dividing by the effective liquid volume of the process tank after water replenishment and drainage correction. The hydrofluoric acid consumption parameter per unit processing area is determined based on the ratio of the change in hydrofluoric acid mass to the processing area in a continuous normal production batch, and is updated after each effective correction and replenishment.

4. The precise fluid replenishment control method for mixed acid solution concentration linkage according to claim 1, characterized in that: The initial parameters of the dual-acid cross-response matrix are determined based on the material balance relationship of the effective liquid volume of the process tank, the mass concentration of hydrofluoric acid stock solution, the mass concentration of sulfuric acid stock solution, the densities of the two stock solutions, and the concentrations of the dual acids before replenishment. The first and second main responses are positive, while the first and second cross-dilution responses are negative. The dimensions of each response are uniformly represented as the change in monoacid mass concentration per unit volume of the original solution.

5. The precise fluid replenishment control method for mixed acid solution concentration linkage according to claim 3, characterized in that, The joint determination of fluid replenishment volume and the determination of the target fluid replenishment sequence include: The final state constraint is that the concentrations of the two monoacids after replenishment are both within their respective target concentration ranges, and the process constraint is that the concentrations of the two monoacids after replenishment of the first stock solution do not exceed their respective process upper and lower limits. The replenishment amounts of the two stock solutions are then determined. Calculate the first trajectory of adding hydrofluoric acid stock solution first and then sulfuric acid stock solution, and the second trajectory of adding sulfuric acid stock solution first and then hydrofluoric acid stock solution. The normalized deviation is obtained by dividing the distance from the single acid concentration in each trajectory to the nearest boundary of the corresponding target concentration interval by the width of the target concentration interval. Trajectories that violate the process constraints are excluded, and the replenishment sequence corresponding to the trajectory with the smallest maximum normalized deviation among the remaining trajectories is determined as the target replenishment sequence.

6. The precise fluid replenishment control method for mixed acid solution concentration linkage according to claim 5, characterized in that: The replenishment volume for each stock solution is divided into pre-replenishment volume and retention / correction volume; When the sum of the repeatability error of automatic potentiometric titration and the flow rate error of the replenishment channel is no greater than 2%, the pre-replenishment volume is 90% of the corresponding original solution replenishment volume; When the sum of the errors is greater than 2% but not greater than 4%, the pre-replenishment volume is 80% of the corresponding original solution replenishment volume; When the sum of the errors is greater than 4%, the pre-replenishment volume is 70% of the corresponding original solution replenishment volume; After the pre-replenishment is completed, the basic circulation time is determined based on the ratio of the effective liquid volume in the process tank to the circulation flow rate, and no less than three basic circulation times are taken as the minimum mixing time. The titration result of the pre-replenishing solution is locked within the shortest mixing time. The lock is released when the shortest mixing time is reached and the rate of change of circulating flow rate and the rate of change of drug solution temperature are both below their respective stability thresholds within two consecutive basic cycles.

7. The precise fluid replenishment control method for mixed acid solution concentration linkage according to claim 6, characterized in that, The formation of the dual-acid responsive fingerprint includes: Obtain the corresponding diacid concentration for the next effective titration after obtaining the pre-replenishment solution; Based on the processing area, liquid volume on the workpiece, drainage volume, and water replenishment volume between the two sampling time points, the change in dual acid concentration caused by non-liquid replenishment factors is calculated. Subtracting the changes in diacid concentrations caused by non-replenishment factors from the diacid concentration differences between the two consecutive tests, we obtain the net response of hydrofluoric acid and the net response of sulfuric acid. The dual-acid response fingerprint is formed by associating the replenishment medium identifier, the commanded replenishment volume, the replenishment pump runtime, the cumulative flow value, the net response amount of hydrofluoric acid, the net response amount of sulfuric acid, the temperature of the drug solution during replenishment, and the effective liquid volume of the process tank according to the same replenishment event.

8. The precise fluid replenishment control method for mixed acid solution concentration linkage according to claim 7, characterized in that: The effective delivery coefficient is the ratio of the magnitude of the actual net response vector of the two acids to the magnitude of the theoretical response vector of the two acids. The theoretical response vector of the two acids is obtained by multiplying the response column vector of the corresponding replenishment channel in the two acid cross-response matrix with the commanded replenishment volume. When the actual net response direction of the two acids is consistent with the direction of the corresponding response column vector, and the effective delivery coefficient is between the 5th percentile and the 95th percentile of the historical normal replenishment event, the corresponding response column vector is updated using the ratio of the actual net response amount of the two acids to the commanded replenishment volume. The updated response column vector is used to determine the replenishment volume for the next replenishment cycle and to predict the intermediate concentration trajectory.

9. The precise fluid replenishment control method for mixed acid solution concentration linkage according to claim 8, characterized in that, The fault determination of the replenishment channel is based on an effective response threshold, which is three times the standard deviation of the corresponding single acid concentration obtained from continuous measurements of the same standard mixed acid sample. The fault determination of the replenishment channel includes: When the actual response direction of the dual acid net is consistent with the theoretical response direction, and the effective delivery coefficient is lower than the lower limit of the normal range, it is determined that there is a delivery attenuation in the replenishment channel, and an inspection command is output indicating that the delivery capacity of the replenishment pump has decreased, the original liquid level is insufficient, there is air in the delivery pipeline, or the opening of the replenishment valve is insufficient. If the target single acid net response quantity does not exceed the corresponding effective response threshold, and the other single acid net response quantity exceeds the corresponding effective response threshold along the main response direction of the other replenishment channel, it is determined that the replenishment valve is cross-connected, the two raw liquid delivery pipelines are reversed, or the raw liquid container is connected incorrectly. If neither the net response of hydrofluoric acid nor the net response of sulfuric acid exceeds its respective effective response threshold, it is determined that the replenishment pump is running dry, the delivery pipeline is blocked, or the replenishment valve is not open. After the fault diagnosis result is generated, the corresponding replenishment pump is stopped and the corresponding replenishment valve is closed.

10. The precise fluid replenishment control method for mixed acid solution concentration linkage according to claim 8, characterized in that: If the next effective titration result shows that the dual-acid response fingerprint is normal and the current concentration of hydrofluoric acid or sulfuric acid has not entered the corresponding target concentration range, the corrected replenishment volume is recalculated based on the updated dual-acid cross-response matrix. When the corrected replenishment amount is not greater than the corresponding retained corrected amount, perform corrected replenishment and re-mixing lock and automatic potentiometric titration; When the corrected replenishment volume is greater than the corresponding retained correction volume, the dual acid intermediate concentration trajectory prediction is re-executed. When the liquid leak detection value reaches the leak alarm threshold or the acid gas detection value reaches the gas alarm threshold, the hydrofluoric acid stock solution replenishment channel and the sulfuric acid stock solution replenishment channel are stopped, and the emergency ventilation is activated.

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