WO2016141649A1

WO2016141649A1 - Chemical liquid dispensing system and flow volume control method

Info

Publication number: WO2016141649A1
Application number: PCT/CN2015/083724
Authority: WO
Inventors: 何金群; 王锐廷; 张豹
Original assignee: 北京七星华创电子股份有限公司
Priority date: 2015-03-10
Filing date: 2015-07-10
Publication date: 2016-09-15
Also published as: CN104681470B; CN104681470A

Abstract

A chemical liquid dispensing system comprises: a liquid storage tank (10) having a return liquid inlet and a liquid outlet; chemical liquid circulation lines having one end connected to the return liquid inlet and the other end connected to the liquid outlet and provided with a circulation pump (11) thereon; chemical liquid output lines having one end connected to the chemical liquid circulation lines and the other end connected to a process unit (14) and provided with a flow volume meter (12) and a valve element (13) thereon, wherein the flow volume meter (12) is used to detect chemical liquid flow volume outputted by the process unit (14); a controller (15) used to control rotating speed of the circulation pump (11). When chemical liquid needs to be delivered to the process unit (14), and before the valve element (13) is switched to enable a transmission path between the flow volume meter (12) and the process unit (14) to be in communication, the controller (15) controls the rotating speed of the circulation pump (11) according to current chemical liquid flow volume detected by the flow volume meter (12). The chemical liquid dispensing system can adjust process flow volume required by the process unit (14) to within a wide range.

Description

Chemical liquid distribution system and flow control method thereof

Technical field

The present invention relates to a semiconductor cleaning machine apparatus, and more particularly to a chemical liquid distribution system for a cleaning machine apparatus and a flow rate control method thereof.

technical background

The chemical liquid distribution system is one of the key systems for the development of single-wafer cleaning equipment. It provides a chemical solution of a certain temperature, pressure and flow that meets the process requirements for the entire equipment, thereby ensuring the uniformity and consistency of the surface corrosion of the wafer. 1 is a schematic view of a prior art chemical liquid distribution system. As shown, the system includes a liquid storage tank 1 that can store a certain amount of chemical liquid and has a liquid return inlet and outlet. a liquid outlet; a circulation line, one end of which is connected to the liquid return inlet of the liquid storage tank 1, and the other end is connected to the liquid outlet; the circulation line is provided with a circulation pump 2, a heater 3, a filter 4, a pressure sensor 5 and a needle in this order. Valve 6. The chemical liquid discharged from the liquid outlet of the liquid storage tank 1 is pressurized by the pump 2, flows through the heater 3, the filter 4, the pressure sensor 5, and the needle valve 6, and returns to the liquid storage tank 1, thereby chemical medicine The liquid can be recycled. Wherein, the heater 3 is used to heat the chemical liquid in the liquid storage tank to a set temperature, the filter 4 is used to filter the particulate impurities in the chemical liquid, and the needle valve 6 is used to adjust the pressure sensor 5 and the liquid storage tank 1 The resistance between the lines makes the pressure sensor 5 have a suitable value. After a period of circulation, the chemical liquid reaches the set temperature, and at this time, the pump 2 is controlled by the speed mode, that is, at the set speed. The flow controller 7 is connected at one end between the needle valve 6 and the pressure sensor 5, and at the other end to the process unit 9 via a pneumatic valve 8. When the process unit 9 needs to use the chemical liquid, the pump 2 is switched to the pressure control mode in advance, that is, the pressure sensor 5 and the pump 2 form a closed loop control, and the pump 2 adjusts the rotation speed according to the pressure detected by the current pressure sensor 5, and the equal pressure. After the pressure value of the force sensor 5 is stabilized, the pneumatic valve 8 is opened, and the flow controller 7 is operated, and the chemical liquid flows out according to the flow rate set by the flow controller 7 to carry out the process. In the pressure control mode, the inlet pressure of the flow controller 7 is ensured to be stable, thereby achieving better process flow stability.

However, since the flow controller 7 is a mature commercial product having a specific flow control range, and the flow control range is often narrow, the process flow range is not well satisfied, and the price is relatively expensive. Therefore, there is a need to provide a chemical liquid flow control method capable of regulating flow rate over a wide range and having a low cost.

Summary of invention

SUMMARY OF THE INVENTION A primary object of the present invention is to provide a chemical liquid dispensing system that is capable of regulating process flow over a wide range and that is inexpensive.

In order to achieve the above object, the present invention provides the following technical solutions:

a liquid storage tank for storing a chemical liquid having a liquid return inlet and a liquid outlet; a chemical liquid circulation line having one end connected to the liquid return inlet and the other end connected to the liquid outlet; the chemical a circulation pump is arranged on the liquid circulation line; a chemical liquid output line is connected at one end to the chemical liquid circulation line, and the other end is connected to the process unit; the chemical liquid output line is provided with a flow meter and the flow Between the connected valve elements, the flow meter is used to detect the chemical liquid flow at the input end of the process unit; the controller is configured to control the rotational speed of the circulating pump; wherein, when the chemical liquid is to be delivered to the Before the process unit is switched, and the valve element is switched to communicate the flow path between the flow meter and the input end of the process unit, the controller controls the chemical liquid flow rate according to the current flow meter detection The speed of the circulating pump.

Preferably, the controller controls when the chemical liquid is not required to be delivered to the process unit The rotation speed of the circulation pump is a set rotation speed.

Preferably, the chemical liquid circulation line is provided with the circulation pump, the heater, the filter, the pressure sensor and the throttle valve in sequence from the liquid outlet.

Preferably, the flow meter is connected at one end to the pressure sensor and the throttle valve, and at the other end to the valve element.

A chemical liquid distribution system, comprising: a liquid storage tank for storing a chemical liquid and having a liquid return inlet and a liquid outlet; a circulation main line, one end of which is connected to the liquid return inlet, and the other end Connected to the liquid outlet; the circulation pipeline is provided with a circulation pump; the circulation branch pipeline has one end connected to the circulation main line and the other end connected to the liquid return inlet; the circulation branch line is provided a flow meter and a valve element connected to the flow meter, the valve element being connected to a process unit, the flow meter for detecting a chemical liquid flow at an input end of the process unit; and a controller for requiring the chemical Before the liquid is delivered to the process unit, and the valve element is switched to connect the flow meter to the transmission path of the input end of the process unit, the circulating pump is controlled according to the flow rate of the chemical liquid detected by the current flow meter. Speed.

Preferably, the controller controls the rotational speed of the circulation pump to a set rotational speed when the chemical liquid is not required to be delivered to the process unit.

Preferably, the chemical liquid circulation line is provided with the circulation pump, the heater, the filter, the pressure sensor and the first throttle valve in sequence from the liquid outlet.

Preferably, the flow meter has one end connected between the pressure sensor and the first throttle valve and the other end connected to the valve element.

Preferably, the valve element is a three-way valve, the input end of which is connected to the flow meter, the first output end is connected to the input end of the process unit, and the second output end is connected to the second throttle valve by the second throttle valve Liquid The mouth is connected.

A flow control method for a chemical liquid distribution system, the chemical liquid distribution system comprising: a liquid storage tank for storing a chemical liquid and having a liquid return inlet and a liquid outlet; a chemical liquid circulation line, one end of which The liquid return inlet is connected, the other end is connected to the liquid outlet, and the chemical liquid circulation line is provided with a circulation pump; the chemical liquid output line is connected at one end to the chemical liquid circulation line, and the other end is connected a process unit is connected, the chemical liquid output line is provided with a flow meter and a valve element connected to the flow meter, the flow meter is used for detecting the chemical liquid flow at the input end of the process unit; and controlling the circulating pump speed Controller. The flow control method includes: when the chemical liquid is to be delivered to the process unit, the controller controls the rotation speed of the circulation pump according to the current chemical flow rate detected by the flow meter; When the flow rate detected by the flow meter reaches a set flow rate, the valve element is switched to communicate the flow path between the flow meter and the input end of the process unit.

Preferably, when the chemical liquid is not required to be delivered to the process unit, a transmission path between the flow meter and an input end of the process unit is cut by the valve element, and the controller is controlled by the controller The rotation speed of the circulation pump is the set rotation speed.

A flow control method for a chemical liquid distribution system, the chemical liquid distribution system comprising: a liquid storage tank for storing a chemical liquid and having a liquid return inlet and a liquid outlet; a circulation main line, one end of which is The liquid return inlet is connected, the other end is connected to the liquid outlet, and the circulation pipeline is provided with a circulation pump; the circulation branch pipeline has one end connected to the circulation main line and the other end connected to the liquid return inlet; a flow meter and a valve element connected to the flow meter are disposed on the circulation branch line, the valve element is connected to the process unit, the flow meter is configured to detect a chemical liquid flow at the input end of the process unit; and control the cycle Pump speed controller. The flow control method includes: when needed When the chemical liquid is delivered to the process unit, the controller controls the rotation speed of the circulation pump according to the flow rate of the chemical solution detected by the current flow meter; and then the flow rate detected by the flow meter reaches the set flow rate. The valve element is switched to communicate the flow path between the flow meter and the input of the process unit.

Compared with the prior art, the chemical liquid distribution system and the flow control method thereof according to the present invention form a closed-loop control of the flow meter and the circulation pump in advance when the chemical liquid is required to be output to the process unit, according to the current flow meter. The detected flow rate adjusts the rotation speed of the circulation pump up to the flow rate set value, and then outputs the chemical liquid, thereby enabling the chemical liquid flow at the input end of the process unit to be quickly stabilized even within a wide range of the flow meter setting value. The ground reaches the set value of the flow; in addition, because the components used in the chemical liquid distribution system are simple in function and low in price, the cost of the entire system is also reduced.

DRAWINGS

1 is a schematic view of a prior art chemical liquid distribution system;

2 is a schematic view of a chemical liquid distribution system according to an embodiment of the present invention;

3 is a schematic view of a chemical liquid distribution system according to another embodiment of the present invention.

Summary of the invention

In order to make the content of the present invention clearer and easier to understand, the following is within the scope of the present invention. For further explanation. Of course, the invention is not limited to the specific embodiment, and general replacements well known to those skilled in the art are also encompassed within the scope of the invention.

Embodiment 1

Referring to FIG. 2, a chemical liquid distribution system according to a first embodiment of the present invention includes a liquid storage tank 10, a chemical liquid circulation line, a chemical liquid output line, and a controller 15. The liquid storage tank 10 stores a chemical liquid inside, a liquid return inlet is arranged at the top, and a liquid outlet is arranged at the bottom. One end of the chemical liquid circulation line is connected to the liquid return inlet of the liquid storage tank 10, and the other end is connected to the liquid outlet of the liquid storage tank 10. The circulation pump 11 is disposed on the chemical liquid circulation line, and the input end thereof is connected to the liquid outlet of the liquid storage tank 10 for driving the flow of the chemical liquid. In the present embodiment, the circulation pump 11 can employ a magnetic pump. The chemical liquid circulation line is provided with a circulation pump 11, a heater 16, a filter 17, a pressure sensor 18, and a throttle valve 19 in this order from the liquid outlet of the liquid storage tank 10. Wherein, the heater 16 is used to heat the chemical liquid in the liquid storage tank 10 to a set temperature; the filter 17 is used to filter particulate impurities in the chemical liquid; the throttle valve 19 can be a needle valve for regulating the pressure The line resistance between the sensor 18 and the return inlet of the reservoir 10 provides a suitable value for the pressure sensor 18. One end of the chemical liquid output line is connected to the chemical liquid circulation line, and the other end is connected to the process unit 14 for transferring the chemical liquid to the process unit 14. As shown, a flow meter 12 and a valve member 13 are provided on the chemical liquid output line. The flow meter 12 is used to detect the flow of chemical liquid at the input end of the process unit 14, one end is connected between the pressure sensor 18 and the throttle valve 19, and the other end is connected to the valve element 13. The valve element 13 serves to shut off or communicate the chemical liquid transport path between the flow meter 12 and the process unit 14. In this embodiment, the valve member 13 can be a pneumatic valve. The controller 15 is used to control the rotational speed of the circulation pump 11, which can set the rotational speed of the circulating pump to a speed control mode and a flow control mode according to process requirements. The speed control mode referred to here is that the circulation pump 11 is operated at the set speed, and the flow control mode is It means that the rotational speed of the circulation pump 11 is controlled according to the flow rate of the chemical liquid detected by the current flow meter 12. Specifically, the controller 15 can implement a closed loop control of the flow meter 12 and the circulation pump 11, and implement a flow control mode for the rotational speed of the circulation pump 11 by an algorithm such as PID or PI.

The controller 15 controls the circulation pump 11 in the following manner:

When it is not necessary to supply the chemical liquid to the process unit 14, the valve element 13 is in a closed state to cut off the transmission path between the flow meter 12 and the input end of the process unit 14, and at this time, the controller 15 controls the rotation speed of the circulation pump 11 to be the set rotation speed. .

When the chemical liquid is to be delivered to the process unit 14, the valve element 13 is switched to the open state, and the controller 15 controls the rotation speed of the circulation pump 11 to be the flow control mode, that is, according to the current flow detection value and the chemical at the input end of the process unit 14. The set value of the chemical flow rate is continuously adjusted to the rotation speed of the circulation pump 11, until the detected value of the flow meter 12 reaches the set value, and then, since the valve element 13 is in the open state, the flow meter 12 and the input end of the process unit 14 The transfer paths are communicated such that the chemical liquid that satisfies the flow setting requirements is output to the process unit 14. Thereafter, the controller 15 always controls the rotation speed of the circulation pump in the flow control mode to ensure that the flow rate of the chemical liquid supplied to the process unit 14 is stabilized to the flow rate set value.

It should be noted that the controller 15 in this embodiment is an element independent of the circulation pump 11, but in other embodiments, the controller 15 may also be integrated in the circulation pump 11, that is, the circulation pump itself has a controller. The function of the present invention is not limited.

From the above, in the present embodiment, when the process unit 14 needs to use the chemical liquid, the circulation pump 11 can adjust the rotation speed according to the current flow rate detected by the flow meter, even if the flow rate setting range required for the process is very large, The flow detection value quickly reaches the flow setpoint required at the input of process unit 14.

Example 2

Fig. 3 is a schematic view showing a chemical liquid dispensing system according to a second embodiment of the present invention.

The chemical liquid distribution system includes a liquid storage tank 20, a circulation main line, a circulation branch line, and a controller 25. The liquid storage tank 20 stores a chemical liquid inside, a liquid return inlet is arranged at the top, and a liquid outlet is arranged at the bottom. One end of the circulation main line is connected to the liquid return inlet of the liquid storage tank 20, and the other end is connected to the liquid outlet of the liquid tank 20 of the storage. The circulation pump 21 is disposed on the circulation main line, and its input end is connected to the liquid outlet of the liquid storage tank 20 for driving the flow of the chemical liquid. In the present embodiment, the circulation pump 21 can employ a magnetic pump. The circulation main line is provided with a circulation pump 21, a heater 26, a filter 27, a pressure sensor 28, and a first throttle valve 29 in this order from the liquid outlet of the liquid storage tank 20. The heater 26 is used to heat the chemical liquid in the liquid storage tank 20 to a set temperature; the filter 27 is used to filter particulate impurities in the chemical liquid; the first throttle valve 29 can be a needle valve for adjusting The line resistance between the pressure sensor 28 and the return inlet of the reservoir 20 provides a suitable value for the pressure sensor 28. One end of the circulation branch line is connected to the circulation main line, and the other end is connected to the liquid return inlet of the liquid storage tank 20. As shown, a flow meter 22, a valve member 23 and a second throttle valve 30 are provided on the circulation branch line. The flow meter 22 is connected between the pressure sensor 28 and the throttle valve 29 at one end, and the process unit 24 is connected to the other end through a valve element 23 for detecting the flow rate of the chemical liquid at the input end of the process unit 24. The valve member 23 can disconnect or communicate the chemical liquid transport path between the flow meter 22 and the process unit 24. In this embodiment, the valve member 23 is a three-way valve, the input end is connected to the flow meter 22, the first output end is connected to the input end of the process unit 24, and the second output end is connected to the liquid storage tank 20 through the second throttle valve 30. The liquid return inlet. The second throttle valve 30 can be a needle valve for balancing the total resistance of the branch at the second output end of the three-way valve 23, so that the pipeline resistance at the two output ends of the three-way valve 23 is the same, that is, the second output end. The resistance between the line and the return inlet is the same as the resistance at the input of the process unit 24. Controller 25 is used to control the rotation speed of the circulation pump 21, which can set the rotation speed of the circulation pump 21 to the speed control mode and the flow control mode according to the process requirements. As in the above embodiment, the flow control mode refers to controlling the rotational speed of the circulating pump 21 according to the flow rate of the chemical liquid detected by the current flow meter 22. Specifically, the controller 25 can form a closed loop control by the flow meter 22 and the circulating pump 21. The flow control mode for the rotation speed of the circulation pump 21 is realized by an algorithm such as PID or PI; the speed control mode means that the circulation pump 21 is operated at the set rotation speed.

The controller 25 controls the circulation pump 21 in the following manner:

When it is not necessary to supply the chemical liquid to the process unit 24, the first output of the three-way valve 23 is closed, cutting off the transmission path between the flow meter 22 and the input end of the process unit 24, at which time the controller 25 controls the circulation pump 21. The speed is the set speed.

When the chemical liquid is to be delivered to the process unit 24, the first output end of the three-way valve 23 is still closed, and the controller 25 controls the rotation speed of the circulation pump 21 to be the flow control mode, that is, according to the current flow detection value and process. The set value of the chemical liquid flow at the input end of the unit continuously adjusts the rotational speed of the circulating pump 21 until the detected value of the flow meter 22 reaches the set value, and then the first output end of the three-way valve 23 is opened to cause the flow meter 22 to The transfer path between the input ends of the process unit 24 is communicated such that the chemical liquid that meets the flow setting requirements is output to the process unit 24. The controller 25 then controls the rotational speed of the circulation pump 21 in the flow control mode to ensure that the flow of the chemical liquid supplied to the process unit 24 is stabilized to the flow rate set value.

The controller 25 in this embodiment is an element independent of the circulation pump 21, but in other embodiments, the controller 25 may also be integrated in the circulation pump 21, that is, the circulation pump 21 itself has the function of a controller, The invention is not limited.

Compared with the first embodiment, the embodiment increases the design of the circulation branch line, in the liquid storage tank 20 After the chemical liquid is pressurized by the circulation pump 21, it passes through the heater 26, the filter 27 and the pressure sensor 28, and then is divided into two paths back to the discharge pipe 20. The second throttle valve 30 of the circulating branch line balances the line resistance of the two output ends of the three-way valve 23, and after the three-way valve 23 is switched to the process unit 23, the line pressure in the circulating branch line remains stable. The detected value of the flow meter that reaches the set flow rate will not fluctuate any more. On the other hand, the chemical liquid in the circulating branch line is heated by the heater 26 to the required process temperature during the cycle, and when the three-way valve 23 is switched to the process unit 23, the heat loss of the line is small, the chemical The temperature change of the liquid is also small.

In summary, the chemical liquid distribution system and the flow control method thereof according to the present invention form a closed-loop control of the flow meter and the circulation pump in advance when the chemical liquid is required to be output to the process unit, according to the current flow meter detection. The flow rate adjusts the rotation speed of the circulating pump up to the flow rate setting value, and then outputs the chemical liquid, so that the chemical liquid chemical process flow at the input end of the process unit can be quickly and stably achieved even within a wide range of the flow meter setting value. The flow setting value; in addition, because the components used in the chemical liquid distribution system are simple in function and low in price, the cost of the entire system is also reduced.

The present invention has been described in terms of the preferred embodiments of the present invention, and the present invention is intended to be illustrative only, and is not intended to limit the scope of the invention. In the case of a number of changes and refinements, the scope of protection claimed in the present invention shall be as defined in the claims.

Claims

A chemical liquid distribution system characterized by comprising:

a liquid storage tank for storing a chemical liquid and having a liquid return inlet and a liquid outlet;

a chemical liquid circulation line, one end of which is connected to the liquid return inlet, and the other end is connected to the liquid outlet; the chemical liquid circulation line is provided with a circulation pump;

a chemical liquid output line, one end of which is connected to the chemical liquid circulation line, and the other end is connected to the process unit; the chemical liquid output line is provided with a flow meter and a valve element connected to the flow meter, the flow rate Used to detect the flow of chemical liquid at the input end of the process unit;

a controller for controlling a rotational speed of the circulating pump;

Wherein, when the chemical liquid is to be delivered to the process unit and the valve element is switched to communicate the flow path between the flow meter and the input end of the process unit, the controller is The flow rate of the chemical liquid detected by the current flow meter controls the rotation speed of the circulation pump.
The chemical liquid dispensing system according to claim 1, wherein said controller controls the rotational speed of said circulating pump to a set rotational speed when said chemical liquid is not required to be delivered to said process unit.
The chemical liquid distribution system according to claim 1, wherein the chemical liquid circulation line is provided with the circulation pump, the heater, the filter, the pressure sensor and the throttle valve in sequence from the liquid outlet. .
The chemical liquid distribution system according to claim 3, wherein one end of the flow meter is connected between the pressure sensor and the throttle valve, and the other end is connected to the valve element.
A chemical liquid distribution system characterized by comprising:

a liquid storage tank for storing a chemical liquid and having a liquid return inlet and a liquid outlet;

a circulating main line, one end of which is connected to the liquid return inlet, and the other end is connected to the liquid outlet; the circulation line is provided with a circulation pump;

a circulation branch line having one end connected to the circulation main line and the other end being connected to the liquid return inlet a flow meter and a valve element connected to the flow meter are disposed on the circulating branch line, the valve element is connected to the process unit, and the flow meter is configured to detect a chemical liquid flow at the input end of the process unit;

a controller that is configured according to the current flow before the chemical liquid is to be delivered to the process unit and the valve element is switched to communicate the flow meter with the transmission path of the input end of the process unit The detected chemical liquid flow rate controls the rotational speed of the circulating pump.
The chemical liquid dispensing system according to claim 1, wherein said controller controls the rotational speed of said circulating pump to a set rotational speed when said chemical liquid is not required to be delivered to said process unit.
The chemical liquid distribution system according to claim 6, wherein the chemical liquid circulation line is provided with the circulation pump, the heater, the filter, the pressure sensor and the first section from the liquid outlet. Flow valve.
The chemical liquid distribution system according to claim 1, wherein one end of the flow meter is connected between the pressure sensor and the first throttle valve, and the other end is connected to the valve element.
The chemical liquid distribution system according to claim 1, wherein the valve member is a three-way valve, the input end of which is connected to the flow meter, and the first output end is connected to the input end of the process unit. The second output is connected to the liquid return port through a second throttle.
A flow control method for a chemical liquid distribution system, characterized in that the chemical liquid distribution system comprises: a liquid storage tank for storing a chemical liquid and having a liquid return inlet and a liquid outlet; a chemical liquid circulation line One end is connected to the liquid return inlet, the other end is connected to the liquid outlet, the chemical liquid circulation line is provided with a circulation pump, and the chemical liquid output line is connected at one end to the chemical liquid circulation line. The other end is connected to the process unit, and the chemical liquid output line is provided with a flow meter and a valve element connected to the flow meter, wherein the flow meter is used for detecting the chemical liquid flow at the input end of the process unit; a controller for circulating pump speed; the flow control method includes:

When the chemical liquid is to be delivered to the process unit, according to the current controller The flow rate of the chemical liquid detected by the flow meter controls the rotation speed of the circulation pump;

Thereafter, when the flow rate detected by the flow meter reaches a set flow rate, the valve element is switched to communicate the flow path between the flow meter and the input end of the process unit.
The flow control method according to claim 10, further comprising: cutting the flow meter and the process unit through the valve member when the chemical liquid is not required to be delivered to the process unit A transmission path between the input terminals, wherein the rotation speed of the circulation pump is controlled by the controller to be a set rotation speed.
A flow control method for a chemical liquid distribution system, characterized in that the chemical liquid distribution system comprises: a liquid storage tank for storing a chemical liquid and having a liquid return inlet and a liquid outlet; a circulation main line; One end is connected to the liquid return inlet, and the other end is connected to the liquid outlet, the circulation line is provided with a circulation pump; the circulation branch line has one end connected to the circulation main line, and the other end is connected with the liquid return inlet Connected to the circulating branch line with a flow meter and a valve element connected to the flow meter, the valve element being connected to a process unit for detecting a chemical liquid flow at the input end of the process unit; a controller that controls the speed of the circulating pump;

The flow control method includes:

When the chemical liquid is to be delivered to the process unit, the controller controls the rotation speed of the circulating pump according to the flow rate of the chemical liquid detected by the current flow meter;

Thereafter, when the flow rate detected by the flow meter reaches a set flow rate, the valve element is switched to communicate the flow path between the flow meter and the input end of the process unit.
The flow control method according to claim 12, further comprising: cutting the flow meter and the process unit by the valve member when the chemical liquid is not required to be delivered to the process unit A transmission path between the input terminals, wherein the rotation speed of the circulation pump is controlled by the controller to be a set rotation speed.