Concentration control system, concentration control method, and program storage medium

Abstract

The present invention provides a concentration control system for providing partial pressure control with a small time delay relative to the actual partial pressure of the gas in the chamber, obtaining an accurate estimated value, and achieving better responsiveness and accuracy than before. The system comprises: a flow control device (1) installed on a supply channel (SL) for supplying gas into the chamber (CN), and controlling the flow rate of the gas flowing through the supply channel (SL) to be the input set flow rate; a partial pressure measuring device (2) for measuring the partial pressure of the gas in the chamber; an observer (3) having a model (31) for estimating the state of the gas in the chamber (CN), which is input with the inflow flow rate of the gas flowing into the chamber and the measured partial pressure of the partial pressure measuring device (2), and outputs the estimated partial pressure of the gas in the chamber (CN); and a controller (4) for setting the set flow rate of the flow control device (1) based on the set partial pressure and the estimated partial pressure of the gas in the chamber (CN) output by the observer (3).

Description

Technical Field

[0001] This invention relates to a concentration control system for controlling the partial pressure of gas within a chamber. Background Technology

[0002] In semiconductor manufacturing processes, a mixed gas, such as a mixture of a raw material gas and a carrier gas, is supplied to the processing chamber at a specified concentration. A mass flow controller, which serves as a flow control device for controlling the flow rate of each gas, is installed on the supply channel, which has multiple branch channels connected to the processing chamber, to control the flow rate of each gas to a specified concentration.

[0003] More specifically, as shown in Patent Document 1, for example, the concentration of the raw material gas in the mixed gas, i.e., the partial pressure of the raw material gas, is determined by an absorption analysis device such as an NDIR (Non-Dispersive Infrared Analyzer) installed in the supply channel upstream of the processing chamber. The partial pressure of the raw material gas measured by the absorption analysis device is fed back, and based on the deviation between the measured partial pressure and the target set partial pressure, the set flow rate of each gas is appropriately adjusted by the flow control device.

[0004] However, since the partial pressure of the gas before entering the chamber is measured in such a concentration control system, if gas adsorption occurs in the flow channel, the measured partial pressure will deviate from the actual partial pressure inside the chamber. Therefore, if the partial pressure is measured in the supply flow channel, it cannot be guaranteed that the actual partial pressure of the gas inside the chamber will remain at the set partial pressure. To solve this problem, it is possible to install an NDIR in the chamber to directly measure the concentration of the gas inside the chamber, thereby controlling the partial pressure more precisely.

[0005] However, NDIR exhibits a significant delay relative to the actual partial pressure and is also noisy. Therefore, even when directly measuring the pressure within the chamber using NDIR, it is impossible to obtain the actual partial pressure change quickly and accurately. Consequently, even with the aforementioned concentration control system, it is difficult to achieve partial pressure control with sufficient response speed and accuracy.

[0006] Existing technical documents

[0007] Patent Document 1: International Publication No. 2010 / 113576 Summary of the Invention

[0008] The present invention was made in view of the above-mentioned problems, and its object is to provide a concentration control system that provides a small time delay relative to the actual partial pressure of the gas in the chamber, can obtain an accurate estimated value, and can achieve better responsiveness and accuracy of partial pressure control than before.

[0009] That is, the concentration control system of the present invention is characterized by comprising: a flow control device disposed on a supply channel for supplying gas into a chamber, wherein the flow rate of the gas flowing through the supply channel is controlled in such a way as an input set flow rate; a partial pressure measuring device for measuring the partial pressure of the gas in the chamber; an observer configured to have a model for estimating the state of the gas in the chamber, the model being input with the inflow flow rate of the gas flowing into the chamber and the measured partial pressure of the partial pressure measuring device, and outputting the estimated partial pressure of the gas in the chamber; and a controller for setting a set flow rate for the flow control device based on the set partial pressure and the estimated partial pressure of the gas in the chamber output by the observer.

[0010] Furthermore, the concentration control method of the present invention is characterized by using a concentration control system comprising: a flow control device disposed on a supply channel for supplying gas into a chamber, wherein the flow rate of the gas flowing through the supply channel is controlled in such a way as an input set flow rate; and a partial pressure measuring device for measuring the partial pressure of the gas in the chamber. The concentration control method includes: using the inflow flow rate of the gas flowing into the chamber and the measured partial pressure of the partial pressure measuring device as inputs to a model of the state of the gas in the chamber, thereby estimating the estimated partial pressure of the gas in the chamber; and setting a set flow rate for the flow control device based on the set partial pressure and the estimated estimated partial pressure of the gas.

[0011] According to this concentration control system, based on the model, the observer outputs the estimated partial pressure of the gas in the chamber. Therefore, by comparing this with the measured partial pressure output by the partial pressure measuring device, a value with minimal delay and low noise relative to the actual partial pressure in the chamber can be obtained. Furthermore, since the observer receives both the inflow rate of the gas flowing into the chamber and the measured partial pressure from the partial pressure measuring device, corrections can be made for deviations from the initial state of the estimated partial pressure and offsets in the partial pressure, resulting in an accurate value. Additionally, since the controller sets the set flow rate of the flow control device based on the estimated partial pressure from the observer, concentration control with better responsiveness than when using the measured partial pressure can be achieved.

[0012] In order to enable the model to more accurately reflect the state within the chamber based on simple mathematical formulas, it is preferable that the model model the conductance of the exhaust channel for discharging gas from the chamber, and that the conductance is set to a fixed value.

[0013] In order to improve the modeling accuracy of the observer even if the flow conductance is a fixed value, it is preferable to provide an exhaust valve configured to control the opening degree on the exhaust channel, the exhaust valve being fixed at a predetermined opening degree.

[0014] To ensure that even if the actual gas partial pressure within the chamber experiences a steady-state offset due to, for example, interference, the value can be reflected in the estimated partial pressure, preferably, the estimated partial pressure is a column vector consisting of a first estimated partial pressure obtained from estimating the actual partial pressure and a second estimated partial pressure obtained from estimating the partial pressure measured by the pressure measuring device. The observer also has a row vector, i.e., the observer gain h, with h1 and h2 as elements, where h2 is set to the same value as the conductance. With this configuration, since the conductance becomes the pole of the controlled object, the steady-state offset can be directly reflected in the first estimated partial pressure through pole configuration.

[0015] If the partial pressure measuring device is an NDIR, and the model is a model that models the delay of the measured partial pressure output by the NDIR relative to the actual partial pressure as a first delay, then partial pressure control can be performed with a value close to the actual partial pressure in the chamber that is practically unobservable.

[0016] To achieve further improved responsiveness by comparing the control with the case where the deviation between the measured partial pressure output by the partial pressure measuring device and the set partial pressure is integrated, it is preferable that the estimated partial pressure is a column vector consisting of a first estimated partial pressure obtained by estimating the actual partial pressure and a second estimated partial pressure obtained by estimating the measured partial pressure by the partial pressure measuring device, and the controller is configured to integrate the deviation between the set partial pressure and the first estimated partial pressure. With this configuration, the responsiveness is improved compared to the case where the measured partial pressure is fed back, because the actual changes in the gas partial pressure within the chamber, which cannot be observed, can be fed back without time delay.

[0017] In order to achieve substantially the same effect as the concentration control system of the present invention in an existing concentration control system, for example by updating the program, it is preferable to use a concentration control system program, which is a program used in a concentration control system comprising: a flow control device disposed on a supply channel for supplying gas into a chamber, and controlling the flow rate of the gas flowing through the supply channel in such a way as an input set flow rate; and a partial pressure measuring device for measuring the partial pressure of the gas in the chamber. The concentration control system program enables a computer to function as both an observer and a controller. The observer is configured to have a model that estimates the state of the gas in the chamber. The model is input with the inflow flow rate of the gas flowing into the chamber and the measured partial pressure of the partial pressure measuring device, and outputs the estimated partial pressure of the gas in the chamber. The controller sets the set flow rate for the flow control device based on the set partial pressure and the estimated partial pressure of the gas in the chamber output by the observer.

[0018] In addition, the program used in the concentration control system can be a program distributed electronically or a program stored on a program storage medium such as a CD, DVD, or flash memory.

[0019] Thus, according to the concentration control system of the present invention, since the observer estimates the partial pressure of the gas in the chamber as the estimated partial pressure based on the model, a value with less noise and time delay can be obtained compared to the measured partial pressure output by the partial pressure measuring device. Therefore, control that immediately reflects the actual concentration change in the chamber can be performed, improving the responsiveness and accuracy of control compared to the past. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating a concentration control system according to one embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram illustrating the state feedback of the observer in the concentration control system using this embodiment.

[0022] Figure 3 This is a block diagram of the state feedback of the observer in the concentration control system using this implementation method.

[0023] Figure 4 This is a graph showing the change in flow conductance of the pressure in each chamber of the exhaust valve in this embodiment.

[0024] Figure 5 This is a block diagram showing the details of the observer in this implementation method, as well as a graph showing the output.

[0025] Figure 6 This is an example of the estimated partial pressure of the gas in the chamber of the observer in this embodiment.

[0026] Figure 7 This is a design example of the observer-controlled poles in this implementation method.

[0027] Explanation of reference numerals in the attached figures:

[0028] 100: Concentration control system; 1: Flow control device; 2: Partial pressure measuring device; 3: Observer; 4: Controller; 11: First flow control device; 12: Second flow control device; 31: Model; 32: Observer gain; CN: Chamber; COM: Control calculation device; EL: Exhaust channel; EV: Exhaust valve; DL1: First branch channel; DL2: Second branch channel; VP: Vacuum pump. Detailed Implementation

[0029] A concentration control system 100 according to one embodiment of the present invention will be described with reference to the figures. The concentration control system 100 of this embodiment controls the partial pressure of a gas in a processing chamber used for plasma treatment of a substrate in a semiconductor manufacturing process, for example. Figure 1 As shown, the chamber CN is connected to a supply channel SL for supplying various gases into the chamber CN and an exhaust channel EL for discharging the gases from the chamber CN to the outside.

[0030] The supply channel SL includes: multiple parallel branch channels DL1 and DL2, each connected upstream to various gas sources; and a converging channel CL, where the branch channels DL1 and DL2 merge into one channel and connect to the chamber CN. In this embodiment, the first branch channel DL1 is connected to a supply source of N2 as a dilution gas, and the second branch channel DL2 is connected to a supply source of CF4 as a processing gas. Furthermore, the type of gas flowing through the supply channel SL is just one example; other gas types are also possible.

[0031] The upstream side of the exhaust channel EL is connected to the chamber CN, and the downstream side is connected to the vacuum pump VP. An exhaust valve EV is installed on the exhaust channel EL to control the flow of the exhaust channel EL. The opening degree of the exhaust valve EV is configured to be controllable to any value between 0% and 100% according to the exhaust valve setting Ex valve set set by the user.

[0032] like Figure 1 As shown, the concentration control system 100 of this embodiment includes: two flow control devices 1, respectively installed on a first branch flow channel DL1 and a second branch flow channel DL2; a partial pressure measuring device 2, installed in chamber CN, for measuring the partial pressure of CF4 gas in chamber CN; a pressure sensor PS, installed in chamber CN, for measuring the total pressure in chamber CN; and a control calculation device COM, for executing the control of each flow control device 1 and the exhaust valve EV, and various calculations. Thus, the concentration control system 100 is configured such that, by utilizing the calculation function of the control calculation device COM to implement an observer 3, the actual partial pressure of CF4 gas in chamber CN, which is normally unobservable, is estimated, and based on the estimated partial pressure and a user-set partial pressure, the set flow rate of each flow control device 1 is changed.

[0033] Each part is described in detail.

[0034] The flow control device 1 is a so-called mass flow controller, which integrates the necessary equipment for flow control, namely, a flow sensor, a valve, and a control board into one device. The control board controls the opening of the valve to minimize the deviation between the measured flow rate determined by the flow sensor and the set flow rate set externally. That is, the flow control device 1 forms a flow feedback loop on a single unit. In this embodiment, the flow control device 1 operates as follows: it receives the set flow rate output by the control calculation unit COM and maintains the flow rate of the gas flowing through each branch channel DL1 and DL2 at that set flow rate. The first flow control device (MFC) 11 installed on the first branch channel DL1 is configured to control the flow rate of N2 gas, and the second flow control device 12 installed on the second branch channel DL2 is configured to control the flow rate of CF4 gas. For the flow sensor, a thermal flow sensor or a pressure flow sensor can be used, and for the valve, various valves such as piezoelectric valves and solenoid valves can be used. Alternatively, a variable orifice can be used instead of a valve to construct the flow control device 1.

[0035] The partial pressure measuring device 2 is a so-called NDIR (non-dispersive infrared analyzer) that measures the partial pressure of CF4 gas in chamber CN based on absorbance. The partial pressure measuring device 2 includes: a light source that emits infrared light into chamber CN; a photodetector that detects the infrared light passing through chamber CN; and a partial pressure calculator (not shown) that calculates the partial pressure of CF4 gas in chamber CN based on the output of the photodetector and according to the absorbance of CF4 gas in chamber CN and the total pressure in chamber CN obtained from a pressure sensor. The partial pressure calculator can be configured, for example, using the calculation function of a control calculation unit COM, but this function can also be implemented using a dedicated calculation board. Furthermore, existing algorithms can be used for the algorithm of the partial pressure calculator to calculate the partial pressure of CF4 gas. In the following description, the partial pressure of CF4 gas output as the measured value in the partial pressure measuring device 2 will also be referred to as the measured partial pressure, so as to distinguish it from the estimated value output by the observer 3. The measured partial pressure output by the partial pressure measuring device 2 has a predetermined time delay relative to the actual partial pressure of CF4 gas in chamber CN and is, for example, superimposed with electrical noise. In other words, it is impossible to directly observe the actual partial pressure of CF4 gas in chamber CN using partial pressure measuring device 2.

[0036] like Figure 2As shown, the control processing unit COM functions as both an observer 3 and a controller 4. The observer 3 simulates the partial pressure state of CF4 within the chamber CN (the controlled object) based on model 31 and outputs a presumed partial pressure. The controller 4 controls the flow control device 1 based on a user-defined partial pressure and the presumed partial pressure output from the observer 3. Specifically, the control processing unit COM includes a CPU, memory, an A / D converter, a D / A converter, and various input / output devices. It executes the concentration control system 100 program stored in the memory, with various devices cooperating to achieve the functions of the aforementioned observer 3 and controller 4.

[0037] Observer 3 is configured as a simulation and Figure 2 The physical characteristics related to the partial pressure of CF4 gas in the chamber CN of the plant, and the estimated partial pressure of CF4 gas in the output chamber CN. Specifically, such as Figure 3 As shown in the block diagram, observer 3 has the ability to be controlled by [the controller]. Figure 2 The device's state equation is the same as that of model 31 and observer gain 32. In the following description, the estimated voltage division output of observer 3 will also be referred to as the estimated voltage division.

[0038] like Figure 3 As shown, the inflow rate of CF4 gas into chamber CN and the partial pressure measurement input model 31 of the partial pressure measuring device 2 are illustrated. Here, the inflow rate of CF4 gas uses the set flow rate Q set input to the second flow control device 12. CF4 Alternatively, the flow rate measured by the flow sensor of the second flow control device 12 can be used as the inflow flow rate. Model 31 outputs a first estimated partial pressure obtained from the actual partial pressure of CF4 gas in the estimated chamber CN and a second estimated partial pressure obtained from the measured partial pressure of the estimated partial pressure measuring device 2, based on the input, as the estimated partial pressure.

[0039] The details of the state equations for Model 31 are explained. Furthermore, as a physical model, it is based on... Figure 1 The physical model shown.

[0040] The total pressure P of chamber CN can be determined relative to the flow rate Q flowing into chamber CN from the supply channel SL. total The flow rate Q from chamber CN through exhaust channel EL vaccum The equation of state for the gas in the chamber CN with volume V is as follows.

[0041] P = 1 / V∫(Q) total —Q vaccum )dt……(A)

[0042] Additionally, if the flow conductance of the exhaust valve EV is set to a fixed value Cv, then

[0043] Q vaccum =Cv*P……(B)

[0044] However, as Figure 4 As shown in the graph, the conductance of the exhaust valve EV has a transitional region, such as the region where the opening of the exhaust valve EV is 20% to 60%, which is greatly affected by the total pressure P in the chamber CN, and a conductance fixed region where the opening is less than 15% and the conductance becomes approximately a fixed value under any total pressure P. In this concentration control system 100, the control arithmetic unit COM adjusts the conditions in a way that models the conductance as a fixed value, which is able to maintain the opening of the exhaust valve EV in the conductance fixed region, for example, less than 15%, so that the conductance is almost unaffected by the total pressure P.

[0045] Furthermore, if we perform a Laplace transform on equation (A) and substitute it into equation (B), then...

[0046] V*P*s=Q total ―Cv*P……(C)

[0047] Transform equation (C) to...

[0048] P = Q total / (V*s+Cv)……(D)

[0049] Additionally, if the flow rate of N2 gas flowing into chamber CN is set to Q... N2 Let the flow rate of CF4 gas flowing into chamber CN be Q. CF4 ,but

[0050] Q total =Q N2 +Q CF4 ……(E)

[0051] According to equations (D) and (E), the transfer function of the partial pressure of CF4 gas in chamber CN is:

[0052] P CF4 (s)=Q CF4 / (V*s+Cv)……(F)

[0053] Furthermore, the partial pressure Con was measured using NDIR, which serves as the partial pressure measuring device 2. CF4 (s) relative to the actual partial pressure P CF4 (s) has a time constant T with a first-order delay, therefore

[0054] Con CF4 (s)=P CF4 (s) / (T*s+1)……(G)

[0055] Based on equations (F) and (G), and in Figure 3 The state equations related to the partial pressures within chamber CN, represented by A, B, and C, are shown in Mathematical Equation 1.

[0056] [Mathematical Expression 1]

[0057]

[0058]

[0059] Therefore, the matrices A, B, and C that determine the state equations are shown in Mathematical Formula 2.

[0060] [Mathematical Expression 2]

[0061]

[0062] like Figure 5 As shown, in order to make the controlled object and the observer 3 the same physical model, the model 31 of the observer 3 is represented by state equations in the common matrices A, B, and C. Hereinafter, the partial pressure measured by the partial pressure measuring device 2 will be recorded as Con. CF4 The first estimated voltage division output of observer 3 is recorded as P^ CF4 The second estimated partial voltage is recorded as Con^ CF4 .

[0063] like Figure 5 As shown in the curve, the measured partial pressure Con output from the partial pressure measuring device 2 CF4 This resulted in time delay and electrical noise. Figure 5 (Noise in the block diagram), but in the second estimated voltage divider Con^ estimated by observer 3. CF4 No electrical noise was superimposed. Additionally, due to the first estimated voltage divider P^ CF4 This represents the actual partial pressure of CF4 gas within the unobservable chamber CN, so the output value also eliminates the time delay.

[0064] Next, the observer gain h[h1; h2] will be explained. The observer gain 32 is the value multiplied by the deviation between the measured voltage division and the second estimated voltage division, and is fed back to model 31. The observer gain 32 is designed through pole placement. Figure 3 The actual steady-state offset Con offset of the controlled object's output is also reflected in the first estimated voltage divider P^. CF4 The output method sets the observer gain h2 to 32. Specifically, since the flow conductance Cv of the exhaust valve EV becomes the pole of the controlled object, h2 is set to Cv as the pole. For example, the simulation results of the estimated voltage divider with Cv=2 and h1=50 are shown in Figure 6It can be seen that even if there is an actual steady-state offset in the output of the controlled object, the first estimated voltage division of observer 3 can reflect the deviation. Furthermore, for h1, any value greater than zero should be set as large as possible.

[0065] Finally, the configuration of controller 4 will be explained.

[0066] like Figure 3 As shown in the block diagram, in this embodiment, the controller 4 is configured not to control the user-set voltage Con set and the voltage measuring device 2's measured voltage Con. CF4 Instead of integrating the deviation, it performs a calculation on the difference between the set voltage Conset and the first estimated voltage P^. CF4 The deviation is integrated. That is, to make the first estimated partial pressure P^ CF4 Feedback is provided by following the set voltage divider (Con set). For poles [f1; f2; -g], the desired response is obtained through pole configuration derived from the state-space representation. Specifically, the observer control with V = 10, Cv = 1, and T = 0.5 can be described by the following state equation: Equation 3.

[0067]

Mathematical Expression 3

[0068]

[0069]

[0070] exist Figure 7 The example shown is a control design based on pole placement according to mathematical formula 3. The simulation results of the response waveforms are compared between the observer control with respect to the partial pressure of CF4 gas in chamber CN, given [f1; f2; -g] = [-100; -20; -2], and the case where the inverse derivative is fed into the output for filtering, as is the case previously. It can be seen that with observer control, noise effects can be eliminated, and the response of the partial pressure can be accelerated. Furthermore, robustness is achieved, so that even if disturbances occur, their effects are not affected.

[0071] Thus, the concentration control system 100 of this embodiment, by obtaining the estimated partial pressure of CF4 gas in the unobservable chamber CN through the observer 3 and controlling the observer in a manner that makes the estimated partial pressure follow the set partial pressure, can achieve high-speed response, compensate for deviations caused by interference offsets, and reduce noise. Therefore, compared with the past, it can accurately control the partial pressure of the gas in the chamber CN at the desired value without time delay.

[0072] Other implementation methods will be described.

[0073] In the described embodiment, the control system is configured to provide state feedback on the partial pressure of CF4 gas, but for example, the control system may also be configured to provide state feedback on the partial pressure of N2 gas.

[0074] Alternatively, the opening degree of the exhaust valve can be left unfixed, and the flow conductance can be defined as a function of the total pressure and the opening degree to construct the observer model.

[0075] When modeling the relationship between the measured partial pressure of the partial pressure measuring device and the actual partial pressure that cannot be observed, the modeling is not limited to a single delay as described in the embodiment. For example, various models such as a double delay can also be performed.

[0076] For the supply channel, there are not limited to two branch channels; there can be three or more. In this case, for the observer model, it is only necessary to model the partial pressure in the chamber according to the flow rate of the gas supplied from each branch channel.

[0077] The measurement principle of the partial pressure measuring device is not limited to absorbance; it can also be a device based on other measurement principles, such as an ultrasonic concentration sensor.

Claims

1. A concentration control system, characterized in that, The concentration control system includes: A flow control device is installed on the supply channel for supplying various gases into the chamber, and controls the flow rate of the various gases flowing through the supply channel in a manner that is the input set flow rate. Partial pressure measuring device, used to measure the partial pressure of various gases in the chamber; The observer is configured to have a model that estimates the state of various gases in the chamber. The model is input with the inflow rate of various gases flowing into the chamber and the measured partial pressure of the partial pressure measuring device, and outputs the estimated partial pressure of various gases in the chamber. as well as The controller sets the flow rate of the flow control device based on the set partial pressure and the estimated partial pressure of various gases in the chamber output by the observer.

2. The concentration control system according to claim 1, characterized in that, The model models the flow characteristics of the exhaust channels for various gases discharged from the chamber. The flow conductance is set to a fixed value.

3. The concentration control system according to claim 2, characterized in that, An exhaust valve is provided on the exhaust channel, and the exhaust valve is configured to control the opening degree, and the exhaust valve is fixed at a specified opening degree.

4. The concentration control system according to claim 2, characterized in that, The estimated partial pressure is a column vector consisting of a first estimated partial pressure obtained by estimating the actual partial pressure and a second estimated partial pressure obtained by estimating the measured partial pressure by the estimated partial pressure measuring device. The observer also has an observer gain h, which is a row vector with h1 and h2 as features. The h2 is set to the same value as the flow conductance.

5. The concentration control system according to claim 1, characterized in that, The partial pressure measuring device is an NDIR. The model is a model that uses the delay of the measured partial voltage of the NDIR output relative to the actual partial voltage as a first delay.

6. The concentration control system according to claim 1, characterized in that, The estimated partial pressure is a column vector consisting of a first estimated partial pressure obtained by estimating the actual partial pressure and a second estimated partial pressure obtained by estimating the measured partial pressure by the estimated partial pressure measuring device. The controller is configured to integrate the deviation between the set voltage and the first estimated voltage.

7. A concentration control method, characterized in that, The concentration control method uses a concentration control system. The concentration control system includes: A flow control device is installed on the supply channel for supplying various gases into the chamber, and controls the flow rate of the various gases flowing through the supply channel in a manner that is the input set flow rate. as well as The partial pressure measuring device measures the partial pressure of various gases within the chamber. The concentration control method includes: The model estimates the state of the various gases within the chamber by inputting the inflow rate of the various gases flowing into the chamber and the measured partial pressure of the partial pressure measuring device; and the estimated partial pressure of the various gases within the chamber is estimated. The flow rate is set based on the set partial pressure and the estimated partial pressure of various gases.

8. A program storage medium storing a program for a concentration control system, characterized in that, The program used in the concentration control system is the program that is used in the concentration control system. The concentration control system includes: A flow control device is installed on the supply channel for supplying various gases into the chamber, and controls the flow rate of the various gases flowing through the supply channel in a manner that is equal to the input set flow rate; and The partial pressure measuring device measures the partial pressure of various gases within the chamber. The concentration control system uses a program to enable the computer to function as both an observer and a controller. The observer is configured to have a model that estimates the state of various gases within the chamber. The model is input with the inflow rate of each gas flowing into the chamber and the measured partial pressure of the partial pressure measuring device, and outputs the estimated partial pressure of each gas within the chamber. The controller sets the flow rate of the flow control device based on the set partial pressure and the estimated partial pressure of various gases in the chamber output by the observer.

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