A control system and method for a plasma source based on frequency clusters

Abstract

This invention discloses a control system and method for a plasma source based on frequency clusters, within the field of plasma source technology. The control system's control unit integrates an LSF load impedance prediction model and a frequency cluster modulation module, controlling the PWM drive unit to output pulse signals; a sustaining circuit maintains stable bus voltage after entering the constant power stage; a sampling unit acquires the resonant output voltage and current; a multi-sensor module monitors the gas flow rate Q, pressure P, and temperature T of the reaction chamber; and the LSF model outputs predicted load impedance values ​​based on Q, P, and T. Z s The frequency cluster modulation module adjusts the switching frequency in segments during the constant power phase. This control system utilizes the LSF load impedance prediction model to achieve accurate prediction of load impedance, and adjusts the switching frequency in segments through the frequency cluster modulation module to achieve a smooth response with no overshoot, accurately adapting to load changes, expanding the process window, and ensuring stable constant power operation of the plasma source.

Description

Technical Field

[0001] This invention relates to the field of plasma source technology, and in particular to a control system and method for a plasma source based on frequency clusters. Background Technology

[0002] In high-end processes such as semiconductor manufacturing and advanced materials processing, plasma sources are crucial due to their ability to generate highly reactive plasma with low ion damage. With the continuous improvement of process precision, the industry generally tends to adopt process conditions with low operating pressure and high input power to achieve higher reaction rates and better process uniformity. However, existing plasma source technologies have the following technical drawbacks under extreme low-pressure, high-power conditions:

[0003] 1. Regarding the narrowing of the process window: In low-pressure environments, the impedance characteristics of plasma are extremely sensitive to changes in operating parameters. When high power is applied, the plasma discharge state is prone to abrupt transitions between multiple stable modes (such as capacitive and inductive modes) or entry into abnormal discharge regions. This nonlinear characteristic leads to a significant narrowing of the parameter range within which the plasma source can operate stably—the "process window." Specifically, the power and pressure matching range required to maintain a specific plasma state is very limited. Any minute parameter fluctuations can cause significant deviations in process results (such as thin film deposition rate and etching uniformity), severely restricting process repeatability and controllability, and failing to meet the stringent requirements of modern semiconductor manufacturing for process uniformity and consistency.

[0004] 2. Regarding power jitter: Under operating conditions, the impedance mismatch between the plasma load and the RF power supply becomes more pronounced, easily leading to power reflection and transmission instability. This instability directly manifests as high-frequency, high-amplitude jitter in the input power. This power jitter causes instantaneous fluctuations in plasma density and active group concentration, creating continuous random interference to the process. Summary of the Invention

[0005] This application provides a control system and method for a plasma source based on frequency clusters, which solves the problems of narrow process window and untimely response to gas load fluctuations in the prior art, and achieves precise adaptation to gas load changes, ensuring stable operation at constant power.

[0006] This application provides a control system for a frequency cluster-based plasma source, including a control unit, a PWM drive unit, a full-bridge inverter circuit, a resonant converter, a transformer, an ignition circuit, a sustaining circuit, a sampling unit, and a multi-sensor module. The control unit integrates an LSF load impedance prediction model and a frequency cluster modulation module. The control unit controls the PWM drive unit to output pulse signals. The PWM drive unit controls the output current of the resonant converter. The resonant converter converts the pulse signals into AC power, providing input to the ignition circuit and sustaining circuit via the transformer. The secondary coil of the transformer is connected to both the ignition circuit and the sustaining circuit. The sustaining circuit maintains stable bus voltage after entering the constant power stage. The sampling unit acquires the resonant output voltage and current. The multi-sensor module monitors the gas flow rate Q, pressure P, and temperature T of the reaction chamber. The LSF model outputs predicted load impedance values ​​based on Q, P, and T. Z s The frequency cluster modulation module adjusts the switching frequency during the constant power phase.

[0007] The beneficial effects of the above embodiments are as follows: the control system can accurately predict the load impedance using the LSF load impedance prediction model under different gas flow rates, gas types and cavity temperature changes, and achieve a smooth response with no overshoot of the switching frequency by segmenting control of the frequency cluster modulation module, accurately adapting to load changes, expanding the process window and ensuring the constant power stable operation of the plasma source.

[0008] Based on the above embodiments, this application can be further improved as follows:

[0009] In one embodiment of this application, the process of fitting the load impedance using the LSF load impedance prediction model is as follows:

[0010] P1: A linear regression model can be used to fit an approximate linear relationship between the load impedance Z and Q, P, and T:

[0011] (4);

[0012] in, k 0 is a constant term. k 1. k 2. k 3 represents the coefficients of the variables fitted using the least squares method;

[0013] P2: Construct the design matrix X and the observation vector Z:

[0014] (5);

[0015] P3: Establish standardized equations:

[0016] The goal of the least squares method is to minimize the sum of squared residuals:

[0017] (6);

[0018] For the variable vector Taking the partial derivatives and setting them to zero, we obtain the standardized equation:

[0019] (7);

[0020] P4: The optimal solution for the parameters is: (8);

[0021] Substituting the optimal solution of the parameters into equation (4) yields the current predicted load impedance value Z. s .

[0022] Technical benefits: The LSF load impedance prediction model, based on linear regression and least squares, can accurately fit the relationship between gas flow rate Q, pressure P, temperature T and load impedance, providing a reliable impedance prediction basis for subsequent control strategies, improving the system's response accuracy to dynamic changes in process parameters, and solving the impedance mismatch problem caused by the limitations of linearization assumptions in traditional control models.

[0023] In one embodiment of this application, the frequency cluster modulation module uses three switching cycles as a frequency cluster, and the frequencies of the first and third switching cycles are... f s ( k The frequency of the second switching cycle is f s ( k +1); No. k Switching frequency at time +1 f s ( k +1) From the frequency at the previous moment f s (k) The derivation leads to:

[0024] (10);

[0025] in, t k+1 for k The cumulative sampling time at time +1 t k for k The cumulative sampling time at any given moment; A is the time-varying frequency factor, and B is the factor affecting the rate of change of the switching frequency. Technical effect: By setting the frequency clusters alternately, the switching frequency overshoot phenomenon is avoided, a smooth switching frequency response is achieved, and the power stability in constant power mode is effectively maintained.

[0026] In one embodiment of this application, the frequency cluster modulation module is in Fixed-frequency control is used, where the fixed-frequency is the switching frequency at time k-1 in the previous frequency cluster, where... Zref Δ is the load impedance corresponding to the preset gas flow rate. dZref This is for load impedance fluctuation error. Technical benefits: Switching to a fixed frequency when the load is stable saves computing resources, reduces switching losses, and improves system efficiency.

[0027] This application also provides a control method for a plasma source based on frequency clusters, which, based on the above-mentioned control system, includes the following steps:

[0028] S1: After the plasma source is powered on, set the gas current excitation threshold. i min And introduce excitation gas;

[0029] S2: Upon receiving the ignition signal, it drives the output relay S to engage, entering the constant current control phase; it then determines the resonant output current. i pri Does it meet the requirements? i min ≤ i pri ≤ i max And it must be maintained above 500ms. If this condition is met, then S3 is executed; otherwise, ignition is considered to have failed.

[0030] S3: Increase the duty cycle to boost power and cycle ignition when ignition is abnormal; disconnect the relay after successful ignition.

[0031] S4: Output the predicted value of the load impedance using the LSF load impedance prediction model. Z s ,when Z s Greater than or equal to Z p At that time, among them Z p Once the critical load impedance value for constant power is reached, the system enters the constant power phase. The control process for the constant power phase is as follows: The output power reference value is... P ref With actual power P o After comparison, the output power error e 0, after power PI modulation, the resonant output current reference value is obtained. i ref , current reference value i ref With the sampled current value i priAfter comparison, the output current error e 1. Output duty cycle via current PI modulator d At the same time, the current error e 1. The switching frequency is obtained by passing the PI modulator and inverting the PI. f s The input frequency cluster modulation module obtains the adjusted switching frequency. Finally, the PWM drive signal is output through the PWM drive unit.

[0032] Technical benefits: This control method is adaptable to different working states of the plasma source: in the constant current stage, it ensures the current conditions for successful ignition; in the constant power stage, it uses the LSF model to predict the impedance and combines frequency cluster modulation to adjust the switching frequency in stages to ensure power stability; at the same time, through dual control of power PI and current PI, it improves the system's dynamic response capability to load changes and solves the problems of power jitter and narrow process window in the existing technology.

[0033] In one embodiment of this application, after introducing the excitation gas in step S1, a stage adjustment is required, specifically: 50ms before the ignition operation, the resonant output current value is adjusted. Reduce to the current set value Technical effect: It can effectively avoid surge current and protect the relay S.

[0034] In one embodiment of this application, the constant current stage control process includes: setting the resonant output current reference value... i ref The current value sampled by the sampling circuit i pri After comparison, the output current error After current PI modulation, the PWM drive unit is activated to output a PWM drive signal. Technical benefits: During the constant current stage, the PWM drive signal is output through current PI modulation to ensure the resonant output current remains stable within the threshold range, preventing excessive current from damaging power devices; simultaneously, it provides stable current conditions for ignition, improving the ignition success rate and ensuring the safe operation of the plasma source during the constant current stage.

[0035] In one embodiment of this application, step S3 specifically involves: if ignition is normal, disconnecting relay S and executing S4; if ignition is abnormal, adjusting the duty cycle during the constant current phase. d After increasing the duty cycle, the ignition is reassessed to ensure it is normal. If it remains abnormal, cyclic ignition is performed until the maximum number of cycles is reached. Technical effect: In case of ignition abnormality, increasing the duty cycle and power for cyclic ignition effectively improves the ignition success rate. If cyclic ignition still fails, an error is reported and the relay is disconnected, preventing equipment damage caused by continuous abnormal system operation and ensuring the safety and reliability of the plasma source. Attached Figure Description

[0036] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0037] Figure 1 This is a structural block diagram of a plasma source control system based on frequency clusters in an embodiment of this application;

[0038] Figure 2 This is a flowchart illustrating the fitting of the load impedance to the LSF load impedance prediction model in an embodiment of this application.

[0039] Figure 3 This is a flowchart of a plasma source control method based on frequency clusters in an embodiment of this application;

[0040] Figure 4 This is a schematic diagram of the k-th frequency cluster of the frequency cluster modulation module in an embodiment of this application;

[0041] Figure 5 This is a comparative schematic diagram of the k-th frequency cluster of the frequency cluster modulation module in the embodiments of this application;

[0042] Figure 6 This is a schematic diagram of the frequency cluster modulation module adjusting the switching frequency in stages in an embodiment of this application. Detailed Implementation

[0043] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0044] Example:

[0045] like Figure 1 As shown, a control system for a plasma source based on frequency clusters includes a control unit (not shown in the figure), a PWM drive unit (not shown in the figure), a full-bridge inverter circuit, a resonant converter, a transformer, an ignition circuit, a sustaining circuit, a sampling unit, and a multi-sensor module. Figure 1 middle, V in For input DC voltage source, V AB This is the output voltage of the full-bridge inverter. i r For resonant current, inductance L r ,L k and capacitor C p To construct a resonant converter (resonant network), the turns ratio of transformer T1 is... n 1; The constant current stage and constant power stage are two control modes within the control unit, used to control the output pulse signal of the PWM drive unit; The LSF load impedance prediction model and the frequency cluster modulation module are algorithm models within the control unit. The LSF load impedance prediction model is used to predict the output load impedance. The frequency cluster modulation module adjusts the switching frequency in segments during the constant power phase.

[0046] The control unit controls the output pulse signal of the PWM drive unit; the PWM drive unit controls the output current of the resonant converter; the full-bridge inverter circuit consists of switching transistors. ST 1- ST 4. Composition: The ignition circuit is connected to the secondary coil N3 of transformer T1. The ignition circuit generates a high-voltage ignition signal, causing the plasma load to oscillate and ionize at high frequency. The resonant converter provides the input AC source. The output current of the resonant converter affects the input current of the ignition circuit. The resonant converter converts the pulse signal output by the PWM drive unit into an AC source and provides the input AC source for the ignition circuit and the sustaining circuit. The sustaining circuit is connected in series with the secondary coil N2 of transformer T, using the vacuum reaction chamber as the secondary side of the high-frequency transformer to only provide sustaining current to the chamber. i o To meet the low-voltage energy input requirement during the ionization sustaining phase; the sustaining circuit is used to maintain bus voltage stability after the transition from the constant current phase (ignition phase) to the constant power phase (ionization phase) when the relay is disconnected; the relay is controlled to engage or disengage by the control unit; the sampling unit is used to collect the ignition current of the ignition circuit and the output voltage V of the resonant converter. loop and output current i pri The multi-sensor module includes a gas flow meter, a pressure sensor, and a temperature sensor to monitor the gas flow rate in the reaction chamber. Q Gas pressure P and reaction chamber temperature T .

[0047] The flowchart of the LSF load impedance prediction model fitting the load impedance is as follows: Figure 2 As shown:

[0048] In plasma systems, gas flow rate Q Gas pressure P and reaction chamber temperature T The effect on load impedance can be described by the following ideal gas model:

[0049] When pumping speedS When fixed, pressure P Proportional to traffic P = Q / S The load impedance Z is proportional to the flow rate and proportional to the temperature. T Inversely proportional to gas flow rate Q For load impedance Z The effect can be expressed by equation (1):

[0050] (1);

[0051] in k Q It is a proportionality constant, which is related to system parameters such as electrode area and collision cross section.

[0052] At a constant temperature, the load impedance is proportional to the pressure: (2);

[0053] in k P It is a proportionality constant, which is related to plasma density and collision frequency.

[0054] Under constant pressure, the load impedance decreases due to the reduced gas density and is inversely proportional to the reaction chamber temperature. (3);

[0055] in k T It is a proportionality constant.

[0056] P1: Define the linear model;

[0057] Combining equations (1), (2), and (3), the load impedance can be fitted using a linear regression model. Z and Q , P , T The approximate linear relationship:

[0058] (4);

[0059] in, k 1, k 2, k 3 represents the coefficient of the variable. k 0 is a constant term; assume that... n Group of observation data ( Q i , P i , t i , Z i ),in The least squares method was used to fit the variable coefficients and constant terms.

[0060] P2: Construct the data matrix and observation vectors;

[0061] Constructing a design matrix X And the observation vector Z:

[0062] (5);

[0063] P3: Establish standardized equations;

[0064] The goal of the least squares method is to minimize the sum of squared residuals:

[0065] (6);

[0066] For the variable vector Taking the partial derivatives and setting them to zero, we obtain the standardized equation:

[0067] (7);

[0068] P4: Solve for the fitting coefficients;

[0069] The optimal solution for the parameters is: (8);

[0070] Substituting the optimal solution of the parameters into equation (4) yields the current predicted load impedance, denoted as . Z s .

[0071] like Figure 3 As shown, a control method for a plasma source based on a variable frequency power cluster includes the following steps based on the aforementioned control system:

[0072] Step S1: After the plasma source is powered on, first set the gas current excitation threshold of the system. i min Excitation gas is introduced, and the phase adjustment unit adjusts the resonant output current value 50ms before ignition. Instantly reduced to the current setting value This can effectively prevent surge current and protect the relay S.

[0073] Step S2: Determine if an ignition signal is received. If an ignition signal is received, drive the output relay S to engage, entering the constant current stage control; otherwise, the system continues to supply excitation gas. The constant current stage control process includes: setting the resonant output current reference value... i ref The current value sampled by the sampling circuit i priAfter comparison, the output current error After current PI modulation, the PWM drive unit is activated to output the PWM drive signal for the inverter switching transistors. D 1~ D 4. When increasing the gas load to boost output power, the duty cycle needs to be increased and the frequency fixed at the resonant frequency. During the constant current stage control, it is necessary to determine whether the following conditions are met. i min ≤ i pri ≤ i max And maintain it above 500ms. If it meets the condition, execute S3; otherwise, consider the ignition failure to have occurred, report a system error, and disconnect relay S.

[0074] Step S3: Determine if ignition is normal; if ignition is normal, disconnect relay S and execute S4; if ignition is abnormal, adjust the duty cycle in the constant current stage. d Increase, so that the resonant output voltage V loop Increase, output power rises, after passing through the coupling transformer T Ignition voltage in the ignition circuit of 1 V cd The number of cycles is increased accordingly, and the ignition is checked again to see if it is normal. If the ignition is still not normal, a cyclic ignition process is performed, with a maximum number of cycles of [value missing]. N This process is repeated to improve the ignition success rate; if ignition still fails after exceeding the cycle limit, it is determined to be an ignition failure, the system reports an error, and the relay S is disconnected.

[0075] Step S4: Output the predicted value of the load impedance using the LSF load impedance prediction model. Z s When the predicted value of the output load impedance Z s Less than Z p At that time, among them Z p The critical load impedance value is the constant power threshold. The plasma source is controlled in the constant current stage. When the gas load continues to increase, causing the output power to be greater than or equal to the power threshold, which is the predicted value of the output load impedance, the critical load impedance value is reached. Z s Greater than or equal to Z p At this point, the plasma source enters the constant power phase. The constant power phase control procedure includes: setting the output power reference value... P ref With resonant output voltage V loop and current i pri The actual power is obtained by multiplying.P o After comparison, the output power error e 0, after power PI modulation, the resonant output current reference value is obtained. i ref , current reference value i ref The current value sampled by the power circuit i pri After comparison, the output current error e 1. Output duty cycle via current PI modulator d Simultaneously, the current error will be... e 1. The switching frequency is obtained by passing the PI modulator and inverting the PI. f s The input frequency cluster modulation module obtains the adjusted switching frequency. Finally, the PWM drive signal for the inverter switching transistor is output through the PWM drive unit. D 1~ D 4, of which D 1~ D 4 is the switching transistor ST 1- ST 4. Drive signal.

[0076] In actual operation, the predicted load impedance fluctuates due to the non-constant process conditions such as gas flow rate, pressure, and temperature. Furthermore, increasing the output power of the plasma source also causes disturbances in the load impedance. In constant power mode, when the gas load continues to increase, the duty cycle needs to be reduced and the frequency increased to maintain power stability; conversely, when the gas load decreases, the frequency decreases and the duty cycle increases to maintain power stability. Frequent disturbances in load impedance cause corresponding changes in the output switch, leading to frequency overshoot and consequently affecting power stability. Therefore, in step S4 of this embodiment, a frequency cluster modulation module is used to adjust the switching frequency.

[0077] Frequency cluster modulation module k A schematic diagram of each frequency cluster is shown below. Figure 4 As shown, the three switching cycles are considered as a frequency cluster, where the frequencies of the first and third switching cycles are... f s ( k The frequency of the second switching cycle is f s ( k +1); No. k Switching frequency at time +1 f s ( k +1) can be obtained by fitting the arctangent function:

[0078] (9);

[0079] in, t k+1 for k The cumulative sampling time at time +1 t 0 represents the initial sampling time. f 0 represents the resonant frequency during measurement; A represents the time-varying frequency factor; and B represents the influence factor on the rate of change of the switching frequency.

[0080] Furthermore, the first k Switching frequency at time +1 f s ( k +1) Available k Switching frequency at any time f s ( k To represent:

[0081] (10);

[0082] Similarly, the first k Switching frequency at any time f s ( k ) can be used k Switching frequency at time -1 f s ( k -1) is used to represent, that is, using the first k -1 hour to the k Predicting the trend of switching frequency at any given time to predict the first k Switching frequency at time +1 f s ( k +1); With the adjustment of the frequency cluster module, the output switching frequency combines the characteristics of the current moment and the next moment, which can more accurately track the changes in load impedance and ensure stable power tracking in constant power mode.

[0083] The above settings (the first one) k Switching frequency at time +1 f s ( k +1) Use the first k Switching frequency at any time f s ( k The advantages of using () to represent () can be seen through comparison; Figure 5 For the frequency cluster modulation module k A comparison diagram of frequency clusters, in the same... k In the frequency cluster, the switching frequency adopts the first frequency. k Frequency of time fs ( k ), then, in the first k In the +1 frequency cluster, the switching frequency adopts the first... k Frequency at time +1 f s ( k+ 1), if the first k Frequency at time +1 f s ( k+ 1) with the k Frequency of time f s ( k If the difference is too large, there is a risk of frequency overshoot, which in turn leads to a sharp power disturbance.

[0084] This embodiment illustrates the staged adjustment of the switching frequency by the frequency cluster modulation module, as shown in the diagram. Figure 6 As shown;

[0085] The system during the ignition phase or the predicted load impedance Z s The critical load impedance value for constant power has not been reached. Z p During the constant current phase, due to the circuit characteristics of the LCL resonant converter, after fixing the hardware parameters such as resistors, inductors, and capacitors, the system operates at the resonant frequency. f A constant current output is performed near 0 to maintain a constant output current and avoid damage to power devices due to excessive current.

[0086] Continuously increase the gas flow rate to reach the constant power critical load impedance value Z p Then, a frequency cluster module is used to adjust the switching frequency. As the gas load continues to increase, the switching frequency increases accordingly in a frequency cluster pattern. When the preset gas flow rate is reached and fluctuates, that is... At that time, among them To account for load impedance fluctuation error, the load impedance corresponding to the preset gas flow rate is set. Z ref This indicates that the predicted load impedance is relatively stable at this point. To save computational resources and reduce switching losses, fixed-frequency control is used within the load impedance fluctuation range, with the frequency being the [number]th [frequency] in the previous frequency cluster. k The switching frequency at time -1. Similarly, as the gas load decreases, the switching frequency decreases accordingly in a frequency cluster pattern until the gas load impedance is less than the constant power critical load impedance value. Z p Enter constant current mode.

[0087] The technical solutions described in the embodiments of this application have at least the following technical effects or advantages:

[0088] 1. The control system can predict the load impedance value using the LSF load impedance prediction model under different gas flow rates, gas types, and chamber temperature variations. Z s The frequency is modulated in stages according to the load impedance value.

[0089] 2. Under the adjustment of the frequency cluster module, the control unit outputs a switching frequency that combines the characteristics of the current and next time moments to achieve a smooth response with no overshoot, accurately adapting to load changes, expanding the process window, and ensuring stable operation at constant power.

[0090] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A control system for a frequency cluster based plasma source, characterized by, The application relates to a high-frequency power supply device for a plasma display panel, which comprises a control unit, a PWM driving unit, a full-bridge inverter circuit, a resonant converter, a transformer, an ignition circuit, a maintenance circuit, a sampling unit and a multi-sensor module; the control unit is internally provided with an LSF load impedance prediction model and a frequency cluster modulation module; the control unit controls the PWM driving unit to output a pulse signal and controls the output current of the resonant converter; the resonant converter converts the pulse signal into an alternating current source, and provides input for the ignition circuit and the maintenance circuit through the transformer; the secondary coil of the transformer is connected with the ignition circuit and the maintenance circuit respectively; the maintenance circuit is used for maintaining the stability of the bus voltage after entering the constant power stage; the sampling unit collects the resonant output voltage and current; the multi-sensor module monitors the gas flow Q, pressure P and temperature T of the reaction cavity; the LSF load impedance prediction model outputs a load impedance prediction value based on Q, P and T Z s ; the frequency cluster modulation module adjusts the switching frequency in sections during the constant power stage. The frequency cluster modulation module takes three switching periods as a frequency cluster, the frequency of the first and third switching periods is f s ( k ), the frequency of the second switching period is f s ( k +1), and the switching frequency at the moment of k +1 is f s ( k +1) is the frequency at the previous moment f s (k) It is derived that: (10)； wherein, t k+1 is k the accumulated sampling time at time t + 1, t k is k the accumulated sampling time at time t; A is a time-varying frequency factor and B is an influence factor of the switching frequency variation rate.

2. The control system of claim 1, wherein: The process of fitting the load impedance by the LSF load impedance prediction model is as follows: P1: The approximate linear relationship between the load impedance Z and Q, P, T can be fitted by using a linear regression model: （4）； wherein, k 0 is a constant term, k 1, k 2, k 3 is a variable coefficient fitted by least squares method; P2: Construct a design matrix X and an observation vector Z: （5）； P3: Establish a standardization equation: The goal of the least squares method is to minimize the sum of squared residuals: （6）； vector of unknowns Taking partial derivatives and setting the derivatives to zero gives the normal equations: （7）； P4: The optimal solution for the parameters is: (8); Substituting the solved parameter optimal solution into equation (4) obtains the predicted value of load impedance Z s .

3. The control system of claim 1, wherein: The frequency cluster modulation module adopts fixed frequency control at The fixed frequency is the switching frequency at the k-1 moment in the previous frequency cluster, wherein, Zref is the load impedance corresponding to the preset gas flow, and dZref is the load impedance fluctuation error.

4. A control method of a frequency cluster-based plasma source based on the control system according to any one of claims 1-3, comprising the following steps: S1: setting a gas current excitation threshold i min and pass in the excitation gas; S2: drive output attraction relay S after receiving the ignition signal, enter constant current stage control; judge the resonance output current i pri whether to meet i min ≤ i pri ≤ i max And maintain above 500 ms, if it is satisfied, S3 is executed, otherwise it is considered that the ignition fails; S3: Increase the duty cycle to increase the power when the ignition is abnormal, and loop the ignition; turn off the relay after the ignition is successful; S4: output the predicted value of load impedance by using LSF load impedance prediction model Z s When Z s greater than or equal to Z p , wherein Z p is the constant power critical load impedance value, enter the constant power stage, and the constant power stage control flow is: compare the output power reference value P ref with the actual power P o , and output the output power error e 0, obtain the resonant output current reference value after power PI modulation i ref , compare the current reference value i ref with the sampled current value i pri , and output the current error e 1, output the duty cycle through the current PI modulator d , and obtain the switching frequency through the PI modulator and take the inverse of the current error e 1 f s , input the frequency cluster modulation module to obtain the adjusted switching frequency , and finally output the PWM driving signal through the PWM driving unit.

5. The control method according to claim 4, characterized in that: In the step S1, after the excitation gas is introduced, a stage adjustment is further needed, specifically: 50 ms before the ignition operation, the resonant output current value is reduced to the current setting value .

6. The control method according to claim 4, characterized by: The constant current phase control flow includes: setting a resonant output current reference value i ref The current value sampled by the sampling circuit i pri Output current error after comparison After current PI modulation, start the PWM drive unit to output the PWM drive signal.

7. The control method according to claim 4, characterized by: The step S3 is specifically: if the ignition is normal, disconnect the relay S and perform S4; if the ignition is abnormal, increase the duty cycle in the constant current stage d If the ignition is still abnormal, the cycle ignition processing is performed until the upper limit of the cycle number.

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