A control method and system for an intermittent steam generator for wafer drying

Abstract

The present invention relates to the field of control, and the present invention relates to a control method and system for an intermittent steam generator for wafer drying, the method comprising: setting the initial number of iterations of an MPC algorithm; optimizing the initial number of iterations to obtain the optimal number of iterations; based on the optimal number of iterations, using the MPC algorithm to control the intermittent steam generator; wherein, collecting temperature data inside a drying box during wafer sample drying to construct a first data sequence; calculating the rate of change of the first data sequence; when the rate of change is less than a preset temperature change threshold, reducing the initial number of iterations; otherwise, calculating the possibility of external interference, and presetting a threshold; when the possibility of external interference is greater than or equal to the preset threshold, reducing the initial number of iterations; otherwise, increasing the initial number of iterations. The present invention reduces the amount of calculation of the MPC algorithm by dynamically adjusting the number of iterations, and applies the MPC algorithm to more accurately control the intermittent steam generator.

Description

Technical Field

[0001] The present invention relates to the field of control and to a control method and system of an intermittent steam generator for wafer drying. Background Art

[0002] With the continuous progress of the semiconductor industry, the processing accuracy and efficiency of wafers are crucial to the performance of the entire industry chain. Wafer drying is one of the key steps in the production process. Its purpose is to remove moisture from the surface and inside of the wafer to ensure the smooth progress of subsequent processes. As a new type of drying equipment, intermittent steam generator has the advantages of high thermal energy utilization, uniform drying, environmental protection and energy saving, so it has broad application prospects in the field of wafer drying.

[0003] At present, a patent application document with publication number CN117712407A discloses a fuel cell water thermal management control method and system based on the MPC algorithm, the method comprising: collecting the real-time inlet and outlet temperatures, power generation current, fan speed and water pump speed data of the fuel cell as the prediction sample space, and establishing a physical model related to the real-time temperature of the fuel cell; establishing the target transfer function of the optimization control model according to the delay of the water thermal management control of the fuel cell system; predicting the temperature trend of the future fuel cell system according to the historical data of the inlet temperature, outlet temperature and the change rate of the fuel cell demand power gain; performing rolling optimization and feedback correction on the prediction model through the MPC algorithm, fusing the predicted temperature change trend with the real data measured by the temperature sensor, and obtaining the optimal output change after fusion; adjusting the speed of the fan and the water pump respectively according to the optimal output change, so as to achieve the effect of real-time temperature control of the fuel cell system.

[0004] The above method uses the MPC algorithm to control the temperature of the fuel cell system, which can effectively suppress the impact of demand current disturbance on the output accuracy of the fuel cell system. However, in the process of rolling optimization of the prediction model, the calculation amount of the MPC algorithm is too large, which may cause the control system to fail to respond quickly, thereby affecting the stability and performance of the control system. Summary of the invention

[0005] In order to solve the technical problem that the calculation amount of the above-mentioned MPC algorithm is too large, which will cause the control system to be unable to respond quickly, thereby affecting the stability and performance of the control system, the present invention provides solutions in the following aspects.

[0006] In a first aspect, a method for controlling an intermittent steam generator for wafer drying comprises:

[0007] Setting the initial iteration number of the MPC algorithm; optimizing the initial iteration number to obtain the optimal iteration number; and controlling the intermittent steam generator using the MPC algorithm based on the optimal iteration number;

[0008] The process of the optimal number of iterations is:

[0009] Collect temperature data inside the drying box during the wafer sample drying process to construct a first data sequence;

[0010] Calculate the change rate of the first data sequence. When the change rate is less than the preset temperature change threshold, reduce the initial iteration number to obtain the optimal iteration number. Otherwise, calculate the possibility of external interference and set the threshold. When the possibility of external interference is greater than or equal to the preset threshold, reduce the initial iteration number to obtain the optimal iteration number: , when the possibility of external interference is less than the preset threshold, increase the number of initial iterations and obtain the optimal number of iterations: ; In the formula, is the optimal number of iterations, is the initial iteration number, is the rate of change, For the possibility of external interference, Represents the ceiling function.

[0011] By adopting the above technical scheme, the initial number of iterations of the MPC algorithm is set for prediction and rolling optimization, the temperature data of actual operation is collected and analyzed, the rate of change of the temperature data is calculated, and a mechanism for dynamically adjusting the number of iterations is initially established. Secondly, whether the interior of the drying box is affected by external interference is considered, and the iteration mechanism is further improved, thereby reducing the calculation amount of the MPC algorithm, and applying the MPC algorithm to more accurately control the intermittent steam generator.

[0012] Preferably, when the rate of change is less than the temperature change threshold, the number of initial iterations is reduced, and the optimal number of iterations is obtained as follows:

[0013] ; In the formula, is the optimal number of iterations, is the initial iteration number, is the rate of change, Represents the ceiling function.

[0014] Preferably, the process of calculating the rate of change of the first data sequence comprises:

[0015] Obtain all extreme value points in the first data sequence, and calculate the degree of change of all extreme value points;

[0016] The change rate of the first data sequence is calculated based on the change degree of all extreme value points. The change rate of the first data sequence is:

[0017] ; In the formula, is the rate of change, For the The degree of change of the extreme point, For the The degree of change of the extreme point, is the total number of extreme points in the first data sequence, It is an exponential function with the natural constant e as its base.

[0018] Preferably, The degree of change of the extreme point for:

[0019] ; In the formula, For the The degree of change of the extreme point, For the The temperature data corresponding to the extreme points, For the The temperature data corresponding to the extreme points, For the The temperature data corresponding to the extreme points, Indicates that in the first data sequence, The number of extreme points intercepted to the left and right with the extreme point as the center.

[0020] By adopting the above technical solution, the degree of change of each extreme point is calculated to evaluate the dynamic change amplitude near the extreme point. Based on the degree of change of the extreme point, the change rate of the entire data sequence is calculated, which helps to understand the overall dynamic characteristics of the data.

[0021] Preferably, the process of calculating the possibility of external interference includes:

[0022] Acquire a second data sequence outside the drying box during the drying process, and calculate a change rate of the second data sequence;

[0023] Performing polynomial fitting on the first data sequence and the second data sequence respectively to obtain corresponding first curves and second curves, and calculating the similarity between the first curve and the second curve;

[0024] The possibility of external interference is obtained by calculating the product of the reciprocal of the absolute value of the difference between the change rate of the first data sequence and the change rate of the second data sequence and the reciprocal of the similarity, and taking the square root of the product.

[0025] By adopting the above technical solution, a second data sequence outside the drying box is obtained, external environmental factors that may affect the drying process are monitored, and the relationship between the internal process and the external environment is analyzed to calculate the possibility of external interference. Based on the evaluation of the possibility of external interference, the number of iterations of the MPC algorithm can be dynamically adjusted to achieve better control effects.

[0026] Preferably, the similarity is:

[0027] ; In the formula, For the similarity, is the value of the temperature change over time of the first curve, is the value of the temperature variation with time of the second curve, is the minimum value of the external temperature of the drying oven, is the maximum value of the external temperature of the drying oven, is the minimum temperature inside the drying oven, It is the maximum value of the temperature inside the drying oven.

[0028] By adopting the above technical solution, the shape difference of two curves can be calculated by integration, so that their similarity or difference can be quantified.

[0029] Preferably, the process of calculating the possibility of external interference includes:

[0030] Acquire a second data sequence outside the drying box during the drying process, and calculate the Pearson correlation coefficient and the root mean square error of the first data sequence and the second data sequence respectively;

[0031] The ratio of the Pearson correlation coefficient to the root mean square error is used as the possibility of external interference.

[0032] By adopting the above technical solution, the ratio of the Pearson correlation coefficient to the root mean square error can also be used as the possibility of external interference, providing a quantitative indicator that comprehensively considers correlation and error.

[0033] In a second aspect, an intermittent steam generator control system for wafer drying includes: a processor and a memory, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, the above-mentioned intermittent steam generator control method for wafer drying is implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] By reading the following detailed description with reference to the accompanying drawings, the above and other objects, features and advantages of the exemplary embodiments of the present invention will become readily understood. In the accompanying drawings, several embodiments of the present invention are shown in an exemplary and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0035] Figure 1 It is a method flow chart of steps S1 to S3 in a method for controlling an intermittent steam generator for wafer drying according to an embodiment of the present invention.

[0036] Figure 2It is a method flow chart of steps S20 to S23 in a method for controlling an intermittent steam generator for wafer drying according to an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0038] The MPC algorithm (model predictive control algorithm) is a model-based closed-loop optimization control strategy. The core of the algorithm is: a dynamic model that can predict the future, online repeated optimization calculations and rolling implementation of control actions and feedback correction of model errors.

[0039] In the implementation of the present invention, the MPC algorithm is applied to the control of the intermittent steam generator, which can achieve accurate control of key parameters such as steam generation, temperature, humidity, etc., thereby improving the uniformity and efficiency of wafer drying. Among them, the rolling optimization feature of the MPC algorithm is one of its core advantages, which allows the controller to update its decision in each iteration to adapt to changes in system status and updates in external conditions.

[0040] The embodiment of the present invention discloses a control method of an intermittent steam generator for wafer drying, referring to Figure 1 , including steps S1 to S3, which are specifically as follows:

[0041] S1: Set the initial number of iterations of the MPC algorithm.

[0042] In an embodiment of the present invention, a temperature sensor is installed in a drying box equipped with an intermittent steam generator, and an initial number of iterations is preliminarily set according to the response speed and control accuracy requirements of the control system of the intermittent steam generator. For example, the initial number of iterations is set .

[0043] S2: Optimize the initial number of iterations to obtain the optimal number of iterations.

[0044] As a computer control algorithm widely used in industrial control, the MPC algorithm is different from the traditional PID algorithm, which only adjusts the parameters according to the control error. Instead, it uses the prediction model of the controlled object to calculate the output value of the system in the future after the control quantity is set, and then adjusts the control quantity in a rolling optimization manner. It has excellent tracking and setting capabilities and system robustness, and can show stable control performance when facing the strong nonlinearity and time-varying characteristics of the actual industrial production process. This rolling optimization feature makes it an iterative process. Each iteration will update the prediction model and optimization problem based on the new system state and external conditions, realizing the rapid response of the MPC algorithm to the dynamic changes of the system and can handle constraint problems. Due to the large amount of calculation of the MPC algorithm, the adjustment of the number of iterations will directly affect the calculation frequency and control response speed of the MPC algorithm. For example, too many iterations may increase the calculation time and resource consumption, while too few iterations may cause the algorithm to fail to converge to a sufficiently accurate solution.

[0045] During the wafer drying process, the temperature change trend in the drying box can reflect the dynamic characteristics of the drying process, such as temperature rise, fall or fluctuation. By analyzing the temperature changes in the drying box, the heat demand and distribution under the current working state can be more accurately reflected. Adjusting the number of iterations based on these data can make the control system more effectively adapt to changes in the actual working environment, thereby improving the stability and performance of the control system.

[0046] Reference Figure 2 , Figure 2 1 is a schematic diagram of a method for obtaining an optimal number of iterations in a control method for an intermittent steam generator for wafer drying according to an embodiment of the present invention, including steps S20 to S23, which are specifically as follows:

[0047] S20: Collect temperature data inside the drying box during the wafer sample drying process to construct a first data sequence.

[0048] The temperature sensor installed in the above step S1 is used to collect temperature data inside the drying box during the process from the start of drying to the end of drying of the wafer sample, wherein the data collection frequency is set to 1 Hz. In addition, the collected data can be preprocessed, including filtering, denoising, etc., to improve the data quality, and the preprocessed temperature data is constructed into a first data sequence in chronological order for subsequent model establishment and analysis.

[0049] S21: Calculate the rate of change of the first data sequence.

[0050] Specifically, in the embodiment of the present invention, all extreme value points in the first data sequence are obtained, and the degree of change of all extreme value points is calculated;

[0051] The change rate of the first data sequence is calculated based on the change degree of all extreme value points, and the change rate of the first data sequence is:

[0052] ; In the formula, is the rate of change, For the The degree of change of the extreme point, For the The degree of change of the extreme point, is the total number of extreme points in the first data sequence, It is an exponential function with the natural constant e as its base.

[0053] Among them, The degree of change of the extreme point for:

[0054] ; In the formula, For the The degree of change of the extreme point, For the The temperature data corresponding to the extreme points, For the The temperature data corresponding to the extreme points, For the The temperature data corresponding to the extreme points, Indicates that in the first data sequence, The number of extreme points intercepted to the left and right with the extreme point as the center.

[0055] For example, take , then The degree of change of the extreme point for:

[0056] ; In the formula, For the The degree of change of the extreme point, For the The temperature data corresponding to the extreme points, For the The temperature data corresponding to the extreme points, For the The temperature data corresponding to the extreme points.

[0057] In another embodiment, the rate of change of the first data sequence also satisfies the following relationship:

[0058] ; In the formula, is the rate of change of the first data sequence, is the temperature change of the first data sequence, is the time variation of the first data sequence, is the total number of time points in the first data sequence, , Respectively , No. The temperature value at a time point, , Respectively , No. The time value corresponding to a time point.

[0059] After obtaining the change rate of the first data sequence, a temperature change threshold is set. In the embodiment of the present invention, the preset temperature change threshold is In other embodiments, a common temperature change threshold range may be determined based on historical experience and experimental data.

[0060] S22: When the rate of change is less than a preset temperature change threshold, the initial number of iterations is reduced to obtain an optimal number of iterations.

[0061] During the wafer sample drying process, when the temperature in the drying box changes relatively steadily, the MPC algorithm does not need to update the control strategy too frequently. At this time, the number of initial iterations is reduced, which saves computing resources while maintaining the stability of the system operation.

[0062] Specifically, when the change rate of the first data sequence is less than the preset temperature change threshold, the initial number of iterations is reduced, and the optimal number of iterations is obtained as follows:

[0063] ; In the formula, is the optimal number of iterations, is the initial iteration number, is the rate of change of the first data sequence, Represents the ceiling function.

[0064] S23: On the contrary, the possibility of external interference is calculated. When the possibility of external interference is greater than or equal to a preset threshold, the initial number of iterations is reduced. When the possibility of external interference is less than the preset threshold, the initial number of iterations is increased to obtain the optimal number of iterations.

[0065] When the temperature changes in the drying box fluctuate, it is necessary to further determine whether these fluctuations are caused by external interference, such as changes in environmental conditions or other system factors. If the fluctuations are caused by external interference rather than internal system problems, reducing the number of iterations can avoid unnecessary response frequencies, thereby improving the stability and energy efficiency of the system; if it is not caused by external interference, the number of iterations needs to be increased to improve the MPC algorithm's response to such fluctuations, achieve rapid convergence, and improve the control efficiency of the intermittent steam generator.

[0066] The difference in temperature inside and outside the drying box can directly reflect the drying box's ability to isolate external interference. If the temperature fluctuations inside the drying box are highly consistent with the outside temperature changes or show a similar trend, it is likely that the thermal insulation performance of the drying box is poor and the outside temperature has a significant impact on the temperature inside the box. At the same time, the temperature change curve can intuitively show the temperature change trend over time. If the temperature change curves inside and outside the drying box are highly similar, it means that the outside temperature change trend has been effectively transmitted to the drying box, which means that the thermal insulation measures of the drying box are not sufficient and have been interfered with by the outside world. Therefore, when the rate of change is greater than or equal to the preset temperature change threshold, the possibility of external interference is calculated. The specific analysis process is as follows:

[0067] In the embodiment of the present invention, a second data sequence outside the drying box during the drying process is obtained, and a change rate of the second data sequence is calculated;

[0068] Performing polynomial fitting on the first data sequence and the second data sequence respectively to obtain corresponding first curves and second curves, and calculating the similarity between the first curve and the second curve;

[0069] Calculate the product of the reciprocal of the absolute value of the difference between the rate of change of the first data sequence and the rate of change of the second data sequence and the reciprocal of the similarity, and take the square root of the product to obtain the possibility of external interference; wherein, the rate of change of the second data sequence can be calculated in the same way as the calculation method of the rate of change of the first data sequence;

[0070] Then the above external interference possibility satisfies the relationship:

[0071] ; In the formula, For the possibility of external interference, is the rate of change of the second data sequence, is the rate of change of the first data sequence, is the similarity between the first curve and the second curve.

[0072] The process of obtaining the similarity between the first curve and the second curve is as follows:

[0073] Perform polynomial fitting on the first data sequence and the second data sequence respectively to obtain the corresponding first curve and the second curve , calculate the first curve and the second curve The area of ​​the enclosed region is then used as the similarity between the two. Then the similarity between the first curve and the second curve satisfies the relationship:

[0074] ; In the formula, For the similarity, is the value of the temperature change over time of the first curve, is the value of the temperature variation with time of the second curve, is the minimum value of the external temperature of the drying oven, is the maximum value of the external temperature of the drying oven, is the minimum temperature inside the drying oven, It is the maximum value of the temperature inside the drying oven.

[0075] In another embodiment, the process of calculating the possibility of external interference may further include:

[0076] Acquire a second data sequence outside the drying box during the drying process, and calculate the Pearson correlation coefficient and the root mean square error of the first data sequence and the second data sequence respectively;

[0077] The ratio of the Pearson correlation coefficient to the root mean square error is taken as the possibility of external interference.

[0078] After obtaining the possibility of external interference, preset the threshold .

[0079] On the basis that the rate of change is greater than or equal to the preset temperature change threshold, when the possibility of external interference is greater than or equal to the preset threshold, the number of initial iterations is reduced, and the optimal number of iterations is obtained as follows:

[0080] ; In the formula, is the optimal number of iterations, is the initial iteration number, is the rate of change of the first data sequence, Represents the ceiling function.

[0081] When the possibility of external interference is less than the preset threshold, the number of initial iterations is increased, and the optimal number of iterations is obtained as follows:

[0082] ; In the formula, is the optimal number of iterations, is the initial iteration number, is the rate of change, For the possibility of external interference, Represents the ceiling function.

[0083] It should be noted that This is to ensure that the degree of reduction in the number of iterations is within [1, 11], so as to avoid the final number of iterations being 0 after reduction.

[0084] S3: Based on the optimal number of iterations, the intermittent steam generator is controlled using the MPC algorithm.

[0085] The optimal number of iterations is obtained according to the above S2, and the intermittent steam generator is controlled using the MPC algorithm. The general control steps are as follows:

[0086] Establish a prediction model. According to the physical characteristics and operating conditions of the intermittent steam generator, establish an accurate prediction model. For example, state space equations or transfer functions can be used to describe the dynamic response of the steam generator under different inputs. Determine the model parameters through system identification methods (such as least squares method) to ensure that the model can accurately reflect the behavior of the actual system. The constraints include upper temperature limit, heating power, etc.

[0087] Rolling optimization, analyzing the temperature change rate in the drying box and the possibility of external interference, selecting the optimal number of iterations corresponding to the above S2, and optimizing within a limited time range in each control cycle according to the current system state and prediction model;

[0088] Implement feedback correction, apply the optimized control input to the actual steam generator, monitor the system output in real time, collect actual temperature data, compare it with the output of the prediction model, and calculate the error. Correct the prediction model according to the error value to improve the prediction accuracy.

[0089] An embodiment of the present invention also discloses an intermittent steam generator control system for wafer drying, including a processor and a memory, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, an intermittent steam generator control method for wafer drying according to the present invention is implemented.

[0090] The system also includes other components familiar to those skilled in the art, such as a communication bus and a communication interface. The configuration and functions of these components are known in the art and will not be described in detail here.

[0091] In the present invention, the aforementioned memory may be any tangible medium containing or storing a program, which may be used by or in combination with an instruction execution system, apparatus or device. For example, a computer-readable storage medium may be any appropriate magnetic storage medium or magneto-optical storage medium, such as a resistive random access memory RRAM (Resistive Random Access Memory), a dynamic random access memory DRAM (Dynamic Random Access Memory), a static random access memory SRAM (Static Random-Access Memory), an enhanced dynamic random access memory EDRAM (Enhanced Dynamic Random Access Memory), a high-bandwidth memory HBM (High-Bandwidth Memory), a hybrid memory cube HMC (Hybrid Memory Cube), etc., or any other medium that can be used to store the required information and can be accessed by an application, a module or both. Any such computer storage medium may be part of a device or accessible or connectable to a device.

[0092] In the description of this specification, "plurality" or "several" means at least two, such as two, three or more, etc., unless otherwise clearly and specifically defined.

[0093] Although this specification has shown and described a number of embodiments of the present invention, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Those skilled in the art will conceive of many modifications, changes and alternatives without departing from the ideas and spirit of the present invention. It should be understood that in the practice of the present invention, various alternatives to the embodiments of the present invention described herein may be employed.

Claims

1. A control method for an intermittent steam generator for wafer drying, characterized in that: include: Set the initial number of iterations of the MPC algorithm; Optimize the initial number of iterations to obtain the optimal number of iterations; Based on the optimal number of iterations, the intermittent steam generator is controlled using the MPC algorithm; The process of obtaining the optimal number of iterations is: Collect temperature data inside the drying box during the wafer sample drying process to construct a first data sequence; The change rate of the first data sequence is calculated. When the change rate is less than the preset temperature change threshold, the initial number of iterations is reduced to obtain the optimal number of iterations: ; On the contrary, the possibility of external interference is calculated and the threshold is set; When the possibility of external interference is greater than or equal to the preset threshold, the number of initial iterations is reduced, and the optimal number of iterations is obtained as follows: , when the possibility of external interference is less than the preset threshold, increase the number of initial iterations and obtain the optimal number of iterations: ; In the formula, is the optimal number of iterations, is the initial iteration number, is the rate of change, For the possibility of external interference, represents the ceiling function; The process of calculating the likelihood of external interference includes: The temperature data outside the drying box during the drying process is obtained as the second data sequence, and its rate of change is calculated; polynomial fitting is performed on the first data sequence and the second data sequence respectively to obtain the corresponding first curve and second curve, and the similarity between the first curve and the second curve is calculated; the product of the reciprocal of the absolute value of the difference between the rate of change of the first data sequence and the rate of change of the second data sequence and the reciprocal of the similarity is calculated, and the square root of the product is taken to obtain the possibility of external interference.

2. The intermittent steam generator control method for wafer drying according to claim 1, characterized in that: The process of calculating the rate of change of the first data sequence comprises: Obtain all extreme value points in the first data sequence, and calculate the degree of change of all extreme value points; The change rate of the first data sequence is calculated based on the change degree of all extreme value points. The change rate of the first data sequence is: ; In the formula, is the rate of change, For the The degree of change of the extreme point, For the The degree of change of the extreme point, is the total number of extreme points in the first data sequence, It is an exponential function with the natural constant e as its base.

3. The control method of an intermittent steam generator for wafer drying according to claim 2, characterized in that: No. The degree of change of the extreme point for: ; In the formula, For the The degree of change of the extreme point, For the The temperature data corresponding to the extreme points, For the The temperature data corresponding to the extreme points, For the The temperature data corresponding to the extreme points, Indicates that in the first data sequence, The number of extreme points intercepted to the left and right with the extreme point as the center.

4. The intermittent steam generator control method for wafer drying according to claim 3, characterized in that: The similarities are: ; In the formula, For the similarity, is the value of the temperature change over time of the first curve, is the value of the temperature variation with time of the second curve, is the minimum value of the external temperature of the drying oven, is the maximum value of the external temperature of the drying oven, is the minimum temperature inside the drying oven, It is the maximum value of the temperature inside the drying oven.

5. The intermittent steam generator control method for wafer drying according to claim 1, characterized in that: The process of calculating the possibility of external interference includes: Acquire a second data sequence outside the drying box during the drying process, and calculate the Pearson correlation coefficient and the root mean square error of the first data sequence and the second data sequence respectively; The ratio of the Pearson correlation coefficient to the root mean square error is used as the possibility of external interference.

6. An intermittent steam generator control system for wafer drying, characterized in that: include: A processor and a memory, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, an intermittent steam generator control method for wafer drying according to any one of claims 1 to 5 is implemented.

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