Temperature control circuit and control method for reaction chamber of remote plasma source

Abstract

The present invention belongs to the technical field of semiconductor manufacturing. Provided are a temperature control circuit and control method for a reaction chamber of a remote plasma source. The circuit comprises a sampling unit, a control unit, a PWM drive unit, a full-bridge inverter circuit and a resonant converter, wherein the sampling unit is used for collecting the output current and output voltage of the resonant converter and the temperature of a chamber; the control unit performs fitting to obtain the temperature of the chamber at a moment k+2, and determines an optimal sequence executed by the PWM drive unit; the PWM drive unit outputs a pulse signal on the basis of the optimal sequence; the full-bridge inverter circuit comprises switching transistors S1-S4, which are controlled to switch on or off on the basis of an output signal of the PWM drive unit; and the resonant converter is connected to the full-bridge inverter circuit, and outputs an alternating-current signal that acts on the reaction chamber. In the present invention, the temperature of a reaction chamber at a moment k+2 can be obtained by means of fitting and is then compared with a preset threshold value, such that a control unit can further determine a regulation value for closed-loop control, thereby ensuring the control effect on the temperature of the chamber, and thus improving the gas dissociation stability of a remote plasma source.

Description

Remote plasma source reaction cavity temperature control circuit and control method

[0001] The present application relates to the technical field of semiconductor manufacturing, in particular to a reaction cavity temperature prediction circuit and control method of a remote plasma source. BACKGROUND

[0002] The remote plasma source is a device for artificially obtaining plasma, commonly used in photovoltaic, chemical, semiconductor and other fields. The remote plasma source mainly consists of a reaction cavity and a power conversion circuit. The power conversion circuit provides power to dissociate gas in the reaction cavity to form plasma. Under the action of airflow, electric field, magnetic field and other factors, plasma and a large amount of heat are formed in the reaction cavity. Excessive temperature can cause the service life of the reaction cavity to decrease, the gas dissociation rate to be low, and the failure rate to be high. The heat control effect of the reaction cavity directly affects the safety of equipment operation.

[0003] At present, the reaction cavity overheating monitoring of the remote plasma generator can only set a threshold value in advance, and the warning is triggered. It has low self-adaptability, weak control precision and no temperature prediction capability, and it is difficult to balance the rapidity, overshoot and stability at the same time, which directly affects the quality and efficiency of the industrial process.

[0004] Therefore, how to more accurately and quickly control the temperature in the reaction cavity in the process of monitoring temperature rise has become a problem to be solved by those skilled in the art. SUMMARY

[0005] In view of the defects in the prior art, the present application provides a remote plasma source reaction cavity temperature control circuit and control method to solve the problem that the temperature of the reaction cavity of the current plasma generator cannot be accurately controlled.

[0006] In a first aspect, the present application provides a remote plasma source reaction cavity temperature control circuit, comprising a sampling unit, a control unit, a PWM driving unit, a full-bridge inverter circuit and a resonant converter,

[0007] The sampling unit is used to collect the output current , output voltage and cavity temperature of the resonant converter.

[0008] The control unit is used to fit the cavity temperature at k+2 time according to the cavity temperature at k time and determine the optimal sequence executed by the PWM driving unit;

[0009] The PWM driving unit is used to output a pulse signal according to the optimal sequence;

[0010] The full-bridge inverter circuit comprises switch tubes S1-S4, which are closed or opened according to pulse signals output by the PWM driving unit.

[0011] The resonant converter and the full-bridge inverter circuit are connected, and an alternating current signal is output to act on the reaction cavity.

[0012] According to the above technical solution, the cavity temperature at the current moment and the primary winding voltage and current of the resonant converter are collected to obtain the cavity temperature at k+2 moment by fitting, the cavity temperature at k+2 moment can be compared with a preset empirical threshold, and then the control unit can further determine the adjustment value of closed-loop control, adjust the pulse signal output by the PWM driving unit, and make the corresponding switch tube in the switch tube S1-S4 closed or opened, so as to ensure the control effect of the cavity temperature.

[0013] Optionally, the resonant converter comprises an LCL resonator and a transformer , the LCL resonator and the transformer are connected, and the LCL resonator and the full-bridge inverter circuit are connected.

[0014] In the second aspect, the present application provides a remote plasma source reaction cavity temperature control method, which is used for the remote plasma source reaction cavity temperature control circuit in any possible implementation manner of the first aspect, and comprises the following steps:

[0015] collecting the cavity temperature at k moment ;

[0016] based on the sampling temperature and a preset thermal equilibrium stable temperature , obtaining the temperature error at k moment ;

[0017] obtaining the cavity temperature at k+1 moment , the primary winding current at k+2 moment and the primary winding voltage at k+2 moment respectively; wherein the cavity temperature is obtained by a PID regulator according to the temperature error at k moment , the opening and closing degree of the cold water flow valve and the duty cycle of the fan are obtained, and the cavity temperature at k+1 moment after the reaction cavity is affected;

[0018] predicting the cavity temperature at k+2 moment and the actual power ;

[0019] according to the absolute value of the temperature error at k+2 moment and a preset threshold value determine an optimal sequence based on a cost function; the optimal sequence outputs a PWM control signal acting on the full-bridge inverter circuit.

[0020] Optionally, the primary winding current at k+2 time is obtained by prediction according to the following formula:

[0021] ;

[0022] The primary winding voltage is obtained by prediction according to the following formula:

[0023] ;

[0024] wherein the root mean square value of the fundamental component of the input square wave voltage , is the DC input of the full-bridge inverter circuit, the characteristic impedance , the quality factor , the resonance frequency , is the switching frequency at k+1 time, is the inductance ratio.

[0025] Optionally, the cavity temperature at k+1 time is obtained by fitting with an arctangent function:

[0026] ,

[0027] wherein, is the cumulative sampling time at k+1 time, is the cumulative sampling time at k time, A is a time-varying temperature factor, and B is an influence factor of the temperature change rate of the reaction cavity temperature.

[0028] Optionally, the cavity temperature at k+2 time and the actual power are predicted by a prediction model,

[0029] The cavity temperature at k+2 time is determined according to the following formula:

[0030] , wherein is the initial sampling time, is the initial temperature of the cavity at the time of measurement;

[0031] The actual power at k+2 time is determined according to the following formula:

[0032] ,in For current With voltage The vector angle.

[0033] Optionally, the temperature error based on time k+2... and preset threshold The relationship between the cost function and the determination of the optimal sequence includes:

[0034] when At that time, the optimal sequence is determined based on cost function one; cost function one ;

[0035] when At that time, the optimal sequence is determined based on cost function two; cost function two , , These are the weighting coefficients for adjusting the temperature of the reaction chamber and the actual power, respectively.

[0036] By adopting the above technical solution, this application has the following beneficial effects:

[0037] (1) This invention collects the cavity temperature and the primary winding voltage of the resonant converter at the current moment. Current It can fit and obtain the cavity temperature at time k+2; the cavity temperature at time k+2 can be compared with the preset empirical threshold, and then the control unit can further determine the adjustment value of the closed-loop control, adjust the pulse signal output by the PWM drive unit, so that the corresponding switch in the switching transistors S1-S4 is closed or opened, ensuring the control effect of the cavity temperature; through two compensation methods, the cavity temperature at time k can be made to track the predicted value at time k+2, and the influence of control delay can be eliminated as much as possible to improve the control accuracy of the cavity temperature.

[0038] (2) The present invention calculates the difference between the reaction cavity temperature predicted by the control unit at time k+2 and the stable temperature thermal equilibrium value, and judges in real time whether the temperature error value of the remote plasma source cavity is greater than the preset threshold. Different cost functions are substituted according to different situations to select the optimal sequence to control the plasma system, which helps to reduce the amount of calculation in the stable temperature prediction process, reduce the computing pressure and power consumption of the processor. Attached Figure Description

[0039] 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.

[0040] Figure 1 shows a schematic diagram of a remote plasma source reaction chamber temperature control circuit provided in an embodiment of the present invention;

[0041] Figure 2 shows a flowchart of a remote plasma source reaction chamber temperature control method provided in an embodiment of the present invention;

[0042] Figure 3 shows a logic block diagram of a remote plasma source reaction chamber temperature control method provided in an embodiment of the present invention;

[0043] Figure 4 shows a schematic diagram of the actual power and actual temperature compensation over time provided by an embodiment of the present invention. Embodiments of the present invention

[0044] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of the present invention and are therefore merely examples, and should not be construed as limiting the scope of protection of the present invention.

[0045] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0046] In one embodiment, as shown in Figure 1, a remote plasma source reaction chamber temperature control circuit is provided, including a sampling unit, a control unit, a PWM drive unit, a full-bridge inverter circuit, and a resonant converter. The sampling unit is used to acquire the primary winding current of the resonant converter. Primary winding voltage and cavity temperature The control unit is used to determine the cavity temperature at time k. Fit the cavity temperature at time k+2 The optimal sequence for the PWM drive unit to execute is determined; the PWM drive unit is used to output pulse signals according to the optimal sequence; the full-bridge inverter circuit includes switching transistors S1-S4, which determine whether to close or open according to the pulse signals output by the PWM drive unit; the resonant converter and the full-bridge inverter circuit are connected to output AC signals to act on the reaction chamber.

[0047] Using the above circuit, the current cavity temperature and the primary winding voltage of the resonant converter are collected. Current The system can fit and obtain the cavity temperature at time k+2. The cavity temperature at time k+2 can be compared with a preset empirical threshold, and then the control unit can further determine the adjustment value of the closed-loop control, adjust the pulse signal output by the PWM drive unit, and make the corresponding switches in the switching transistors S1-S4 close or open, so as to ensure the control effect of the cavity temperature.

[0048] Specifically, the resonant converter also includes an LCL resonator and a transformer. The LCL resonator is connected to the full-bridge inverter circuit, and the transformer is... Connected to an LCL resonator. An LCL resonator includes an inductor. , and capacitor ,transformer This is a high-frequency transformer with a turns ratio of n:1, which achieves efficient energy transfer and reduces costs through transformer coupling. The reaction chamber includes inlet / outlet channels and water channels, and the gas load is... .

[0049] In this system, the cavity temperature at time k+2 can be fitted by a predictive model. The predictive model is indispensable for the implementation of MPC (Multi-Process Control). It is a model describing the operating state of an object, aiming to accurately predict the future state of the system output within the control time domain. It can predict the output state of the system at time k+1 using the system's state at time k, making the output value of the control variable at the next time step closer to the desired value, thus achieving better control performance. As the name suggests, the predictive model is for predicting and controlling the state of the system, so it is not bound by the model form or emphasizes the model structure; as long as it can clearly express the input and output relationship of the control variable, it is feasible. Common predictive models fall into two categories: parametric models represented by state equations and transfer functions; and non-parametric models represented by impulse responses or step signals.

[0050] In this embodiment, the prediction model selected is a state-space equation, and its discretized form obtained from the system transfer function is as follows:

[0051] (1)

[0052] Where A, B, and C are the coefficient matrices of the controlled system; For state variables, For output quantity, This refers to the input quantity, i.e., the control quantity; , These are the state and input quantities at times k+1 and k, respectively.

[0053] The control model makes predictions based on formula (1), and the process is as follows:

[0054] (2)

[0055] In formula (2): P is the prediction step size; y(k+j / k) is the output at time k+j; u(k+1 / k) is the input at time k+1.

[0056] Rewrite formula (2) in matrix form:

[0057] (3)

[0058] in, ; ;

[0059] ; .

[0060] In one embodiment, a remote plasma source reaction chamber temperature control method is provided, which is used in the remote plasma source reaction chamber temperature control circuit provided in the above embodiment, as shown in Figure 2, including:

[0061] S1. Collect the cavity temperature at time k. .

[0062] S2. Based on sampling temperature and the preset thermal equilibrium stable temperature Obtain the temperature error at time k. .

[0063] S3. Obtain the cavity temperature at time k+1. and the primary winding current at time k+2 Primary winding voltage Among them, cavity temperature The PID controller is based on the temperature error at time k. The opening and closing degree of the cold water flow valve and the duty cycle of the fan are obtained and applied to the reaction chamber at time k+1.

[0064] The current sampling temperature Compared to the thermal equilibrium stable temperature, the output temperature error After passing through the PID controller, the opening degree of the cooling water flow valve and the fan duty cycle are obtained and applied to the reaction chamber. After multi-step fitting, the chamber temperature at time k+1 is output. For the model prediction unit; similarly, the primary winding current. ,Voltage It was also obtained through fitting.

[0065] As shown in Figure 3, the cavity temperature at time k+1 The following is obtained by fitting the arctangent function:

[0066] (4)

[0067] in, The cumulative sampling time at time k+1 The initial sampling time, A represents the initial temperature of the cavity during measurement; A is the time-varying temperature factor; and B is the factor influencing the rate of temperature change of the reaction cavity.

[0068] Furthermore, the reaction chamber temperature at time k+1 The cavity temperature at time k can be determined. To indicate:

[0069] (5)

[0070] in, The cumulative sampling time at time k+1 Let k be the cumulative sampling time at time k.

[0071] For LCL circuits, due to the resonant effect of the converter, the resonant frequency of the converter is defined. and switching frequency normalized value They are respectively:

[0072] ; (6)

[0073] The equivalent resistance and the root mean square value of the fundamental component of the input square wave voltage are expressed as follows:

[0074] ; (7)

[0075] Where fs is the output frequency; its equivalent circuit has an inductance ratio and characteristic impedance. And quality factor Q

[0076] ; (8)

[0077] (9)

[0078] It can be seen that the primary winding current and voltage They are respectively:

[0079] (10)

[0080] (11)

[0081] Primary winding current at time k+2 Predicted using the following formula:

[0082] (12)

[0083] Primary winding voltage at time k+2 Predicted using the following formula:

[0084] (13)

[0085] For an LCL resonant network, the root mean square value of the fundamental component of the input square wave voltage is... , The characteristic impedance is the DC input of the full-bridge inverter circuit. Quality factors resonant frequency , The switching frequency at time k+1. This is the inductance ratio.

[0086] S4. Predict the cavity temperature at time k+2. and actual power .

[0087] Specifically, the cavity temperature at time k+2 and actual power The cavity temperature at time k+2 is predicted by the predictive model. The cavity temperature at time k+1 can be obtained and the cavity temperature sampled at time k To represent, specifically determined according to the following formula:

[0088] (14)

[0089] in The initial sampling time, The initial temperature of the cavity during measurement;

[0090] The actual power at time k+2 Determined according to the following formula:

[0091] (15)

[0092] in For current With voltage The vector angle, taking values ​​of .

[0093] S5. Based on the absolute value of the temperature error at time k+2 and preset threshold The optimal sequence is determined based on the cost function; the PWM control signal output by the optimal sequence is applied to the full-bridge inverter circuit.

[0094] in, For the predicted cavity temperature at time k+2 and temperature thermal equilibrium stability value The difference between them.

[0095] Specifically, step S5 includes:

[0096] when At that time, the optimal sequence is determined based on cost function one; cost function one ;

[0097] when At that time, the optimal sequence is determined based on cost function two; cost function two , , These are the weighting coefficients for adjusting the temperature of the reaction chamber and the actual power, respectively.

[0098] Output sequence , , , The optimal sequence is then optimized by substituting the corresponding cost function into the rolling optimization process. The minimized cost function outputs the optimal sequence to the PWM drive unit, which generates pulse signals to control the switching transistors of the corresponding full-bridge inverter circuit to open or close. Based on this, closed-loop multi-step predictive control of the reaction chamber is achieved, minimizing the impact of control delay and improving the precision of chamber temperature control.

[0099] Understandable, This indicates that switches S1 and S3 are on; This indicates that switches S1 and S4 are on. , And so on.

[0100] As shown in Figure 4, power tracking control is performed based on cost functions G1 and G2, therefore the actual power... Capable of tracking the preset reference power at all times For cavity temperature control, the temperature rise of the reaction cavity is monitored, and a corrected control matching result is generated based on the monitoring result. The difference between the actual temperature and the preset thermal equilibrium temperature is compared with a preset threshold to facilitate subsequent compensation and adjustment of the cavity temperature and to regulate the heat dissipation system.

[0101] The above embodiments are only used to provide a detailed description of the technical solutions of this application. However, the descriptions of the above embodiments are only for the purpose of helping to understand the methods of the embodiments of the present invention and should not be construed as limiting the embodiments of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art should be covered within the protection scope of the embodiments of the present invention.

Claims

1. A remote plasma source reactor chamber temperature control circuit, comprising: The circuit comprises a sampling unit, a control unit, a PWM driving unit, a full-bridge inverter circuit and a resonant converter, The sampling unit is configured to sample a primary winding current of the resonant converter primary winding voltage and cavity temperature ； The control unit is configured to determine the cavity temperature at the kth moment in time , fit the chamber temperature at time k+2 and determining an optimal sequence executed by the PWM driving unit; the PWM driving unit is configured to output a pulse signal according to the optimal sequence; the full-bridge inverter circuit comprises switching tubes S1-S4, which are closed or opened according to the pulse signal output by the PWM driving unit; the resonant converter is connected with the full-bridge inverter circuit and configured to output an alternating current signal to act on the reaction cavity.

2. The circuit of claim 1, wherein, The resonant converter includes an LCL resonator and a transformer The LCL resonator and transformer are connected, the LCL resonator and the full-bridge inverter circuit are connected.

3. A method for temperature control of a remote plasma source reactor chamber, comprising: The remote plasma source reaction cavity temperature control circuit according to any one of claims 1-2 comprises: collecting the cavity temperature at time k ； based on the sampling temperature and a preset thermal equilibrium stable temperature , the temperature error at time k is obtained ； obtaining the cavity temperature at k+1 time , and the primary winding current at k+2 time instant primary winding voltage ; wherein the cavity temperature for the PID regulator according to the temperature error at the time k obtaining the opening degree of the cold water flow valve and the duty cycle of the fan, and applying the obtained opening degree and duty cycle to the cavity temperature at the k+1 time point after the reaction cavity is acted on; Predicting the chamber temperature at time k+2 and actual power ； According to the absolute value of the temperature error at k+2 time and a preset threshold value determining the optimal sequence based on a cost function according to the relationship between the PWM control signal output by the optimal sequence and the full-bridge inverter circuit.

4. The method of claim 3, wherein, primary winding current at time k+2 is obtained by the following equation: ； Primary winding voltage The prediction is obtained according to the following formula: ； wherein the root mean square value of the fundamental component of the input square wave voltage is ， DC input for full-bridge inverter circuit, characteristic impedance , quality factor , resonance frequency ， for the switching frequency at k+1 time instant, is the inductance ratio.

5. The method of claim 4, wherein, Cavity temperature at time k+1 Fitted from arctangent function: ， wherein, cumulative sampling time for k+1 time instant, is the cumulative sampling time at the k time point, A is a time-varying temperature factor, and B is an influence factor of the temperature change rate of the reaction cavity temperature.

6. The method of claim 5, wherein, k+2 time chamber temperature and actual power predicted by the prediction model, k+2 time of cavity temperature is determined according to the following formula: wherein for the initial sampling time, is the initial temperature of the cavity when the measurement is performed; actual power at k+2 time instant is determined according to the following formula: wherein for current With voltage is the vector angle of the reference power and the actual power.

7. The method of claim 6, wherein, The temperature error at the k+2 moment And a preset threshold The relationship, the optimal sequence is determined based on the cost function, including: When at a time, the optimal sequence is determined based on a cost function one; the cost function one ， is the reference power. When at the time, the optimal sequence is determined based on a cost function two; the cost function two ， 、 are weight coefficients for adjusting the reaction cavity temperature and the actual power, respectively.

Images