JP2000018408A - Mass flow control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cost-reduced mass flow controller system. SOLUTION: This mass flow control system uses a mass flow controller comprised of a valve system with a valve element and a valve seat, and a mass flow control system, where mass flow is controlled by changing a position of an appropriate valve element based on an output from a sensor. In this control system, two or more independent mass flow controllers 15A, 15B, 15C and 15D, and one controller for these two or more mass flow controller 15A, 15B, 15C and 15D are equipped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a mass flow control system using a mass flow controller used in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art Generally, in a semiconductor manufacturing process or the like, a mass flow control valve called a mass flow controller is widely used because it is necessary to precisely adjust a flow rate when supplying various kinds of process gases. Conventionally, this mass flow controller is composed of a valve mechanism and a control mechanism,
The valve mechanism includes a flow path through which the fluid passes, a valve element that changes the opening degree of the flow path, a driving unit that drives the valve element, and a sensor that detects a fluid flow rate in the flow path. . In addition, the control mechanism includes a bridge circuit that takes in a detection signal from the sensor and outputs a flow signal, a comparison circuit that compares the flow signal with a predetermined setting signal and outputs a correction signal, and a control circuit based on the correction signal. And a drive circuit for outputting a drive signal to the drive unit. In the conventional mass flow controller, the valve mechanism and the control mechanism are housed in the same casing.

However, in the semiconductor manufacturing process, corrosive gas or the like is used, and corrosive gas flows through the valve mechanism of the mass flow controller. Therefore, there is a problem that the control mechanism may be damaged by the corrosive gas. . In order to solve the problem, for example, Japanese Patent Application Laid-Open No. Hei 6-83456 proposes that the control mechanism be housed in a casing different from the casing in which the valve mechanism is housed.

[0004]

However, the technique disclosed in Japanese Patent Application Laid-Open No. 6-83456 has the following problems. (1) Since each mass flow controller has a control mechanism individually, there is a problem that the price of the mass flow controller is high. In addition, the valve mechanism is susceptible to corrosion due to the flow of corrosive gas and the like, and if a gas of crystallinity is flowed, the pipe for the sensor may be clogged. There was a problem that even if the mechanism was not damaged, it was replaced together.

(2) Further, the valve mechanism includes a valve section having a valve element and a valve seat, and a sensor section, which are housed in one casing. And since a valve part differs according to the kind and flow rate of gas, there are only kinds of valve parts corresponding to the kind and flow rate of gas. In addition, since the sensor unit differs depending on the type and flow rate of the gas, there are only types of sensor units corresponding to the type and flow rate of the gas. And, as replacement parts of the mass flow controller, there are types corresponding to multiplication of the type of the valve unit and the type of the sensor unit, and it is difficult to prepare them as replacement parts.

An object of the present invention is to solve the above-mentioned problems and to provide a mass flow controller system with reduced cost.

[0007]

To achieve the above object, a mass flow controller system according to the present invention has the following configuration. (1) a valve mechanism including a valve body, a valve seat, and a flow sensor;
A mass flow control system using a mass flow controller including a control mechanism for controlling a mass flow rate of a fluid by obtaining an output of the flow rate sensor unit and changing a position of the valve body, and exists independently. It has two or more valve mechanisms and one control mechanism for controlling the two or more valve mechanisms. (2) In the mass flow control system described in (1), the valve unit including the valve body and the valve seat and the sensor unit are housed in separate casings, and the sensor unit is separated from the valve unit. It can be exchanged.

The operation of the mass flow control system having the above configuration will be described. Usually, in a semiconductor process, 4 to 8 mass flow controllers are often used at the same place, and they are put together to constitute a unit. Here, these mass flow controllers have only a valve mechanism, and as a control mechanism, one control mechanism is housed in a casing different from the mass flow controller and is attached to the unit. 4-8
When controlling the individual valve mechanisms, sampling control can be performed at intervals of about 10 msec, which is sufficient as the sampling interval of the mass flow controller currently used. One control mechanism, cpu, controls each valve mechanism by sequentially sampling 4 to 8 valve mechanisms.

[0009] Compared with the conventional mass flow controller, only one control mechanism is required. Therefore, even if a high-performance cpu is used as the control mechanism, the cost can be reduced. Further, even when the sensor unit is clogged and the valve mechanism is replaced, there is no need to replace the control mechanism, so that there is no waste. Further, in the valve mechanism, if the valve portion and the sensor portion are separately housed in separate casings so that each can be replaced as a separate body, the type of the valve portion and the type of the sensor portion can be replaced. Can be prepared, so that the types of replacement parts to be stocked can be reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying a mass flow controller system according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is an overall configuration diagram of a mass flow controller system according to one embodiment of the present invention.
Is shown in the block diagram. It is a gas supply unit for supplying four types of process gas, and is composed of four lines A to D. Since the four lines have the same configuration, the A line will be described. The left end is the input side,
An input port of the regulator 11A is connected to a process gas supply source. The regulator 11 keeps the supply pressure of the process gas supplied to the mass flow controller constant. The output port of the regulator 11A is connected to the input port of the shutoff valve 14A. Further, a pressure sensor 12A for detecting the pressure of the process gas and a monitor 13A for monitoring the detected pressure are connected to a pipe in the middle of the connection between the regulator 11A and the shutoff valve 14A.

The output port of the shutoff valve 14A is
It is connected to the mass flow controller 15A. The mass flow controller 15A includes a sensor unit 16A that detects the mass flow rate of the process gas flowing through the mass flow controller in real time, and a valve unit 17A that changes the flow rate of the process gas. The output port of the mass flow controller 15A is connected to the input port of the shutoff valve 18A. The output port of the shutoff valve 18A is connected to a vacuum chamber (not shown).

FIG. 2 shows a specific configuration example of the sensor section 16 and the valve section 17 constituting the mass flow controller 15. The proportional valve main body 23 is hollow, and a diaphragm 24 is provided at the center of the hollow portion in a state where the diaphragm 24 is fixed around the proportional valve main body 23. At the center of the diaphragm 24, a valve stem 25 for connecting the diaphragm 24 and the valve body 37 is provided. A return spring 18 is attached to the proportional valve main body 23 above the diaphragm 24,
The diaphragm 24 is urged downward by a return spring 28. The return spring 28 used in the present invention uses a considerably strong spring in order to obtain a higher breaking performance than a return spring used in a conventional proportional solenoid type mass flow controller.

A diaphragm 24 for preventing compressed air from leaking is provided at an intermediate position of the valve rod 25 with its periphery fixed to the proportional valve body 23. Thus, the compressed air supplied from the compressed air supply hole 19 formed on the side surface of the proportional valve body 23 acts to move the valve rod 25 upward. The proportional valve body 23 is attached to the body 38. In the center of the body 38, the valve input port 26
Are formed. On the right side of the valve input port 26, a valve output port 21 is formed. The valve output port 21 is
It communicates with the mass flow controller outlet 22. At the upper end of the valve input port 26, a valve seat 27 is formed.
At the left end of the body 38, a flow path changing block 29 is attached. In the flow path changing block 29, a right angle flow path 30 is formed.

Next, the configuration of the mass flow meter unit 2 will be described.
The main flow path block 52 constituting the sensor section 16 has a mass flow controller inlet 41 opened on the left side of the main flow path 43. Further, a columnar member 42 for keeping the flow of the fluid in a laminar state is held at a central portion of the main flow path 43 with a predetermined distance from the inner wall. A conduit inlet 44 and a conduit outlet 46 are opened on the inner wall of the main channel 43 on both sides of the columnar member 42, and a conduit 45 is provided so as to communicate between the conduit inlet 44 and the conduit outlet 46. In order to accurately measure the mass flow rate with good responsiveness, it is necessary to accurately supply a constant ratio of fluid to the total mass flow rate of the fluid. Therefore, it is necessary to keep the fluid flowing through the main flow path 43 and the conduit 45 in a laminar state. At the right end of the main flow path block 52, a flow path change block 47 is attached. The flow path changing block 47 has a right angle flow path 48 formed therein. At the left end of the main flow path block 52, a flow path change block 49 is attached. The flow path changing block 49 has a right angle flow path 50 formed therein. The flow path changing block 47 is attached to the flow path block 29 from the upper side to the lower side by the two connection bolts 51. Thereby, the sensor unit 16 is detachably attached to the valve unit 17.

The sensor section 16 is composed of a conduit 45 and a pair of self-heating type thermometers having a large temperature coefficient wound on the upstream side and the downstream side of the conduit 45 through which a fluid flows. It is configured. Here, the fluid F flows inside the conduit 45 in the direction indicated by the arrow. Conduit 45
A heat-sensitive resistance wire having a diameter of 25 μm is placed upstream and downstream of
Two heat-sensitive coils R1 and R2 are formed by winding 0 turns. The heat-sensitive resistance wire is made of a material having a large temperature coefficient, such as iron or a nickel alloy. Thermal coil R1, R
Numeral 2 is adhered to the conduit 1 with a UV curable resin or the like to form a sensor unit. Then, a bridge circuit is formed by the heat-sensitive coils R1 and R2, the temperature of the heat-sensitive coils R1 and R2 is controlled to a constant value, and the mass flow rate of the fluid is calculated from the potential difference between the bridge circuits.

Next, the configuration of the control unit of the mass flow controller will be described. The heat-sensitive coils R1 and R2 are connected to the amplifier 31 respectively. The amplifier 31 is connected to the control means 32. The control means 32 is connected to a central control device (not shown). The control unit 32 receives an input signal S from the central control unit. The control means 32 is connected to the pulse conversion circuit 33. The pulse conversion circuit 33 is connected to each coil of the supply solenoid valve 35 and the exhaust solenoid valve 36. On the other hand, a supply source 34 of compressed air is connected to an input port of the supply solenoid valve 35. The output port of the supply solenoid valve 35 is connected to the compressed air supply hole 40. The input port of the exhaust solenoid valve 36 is also connected to the compressed air supply hole 40. And the exhaust solenoid valve 3
The output port 6 is connected to the exhaust pipe.

Next, the operation of the sensor section 16 and the valve section 17 of this embodiment will be described. FIG. 2 shows a state where compressed air is not supplied to the mass flow controller. At this time, the cutoff signal is input to the control means 32 as the input signal S. The control means 32 receives the cutoff signal, and, through the pulse conversion circuit 33,
5 and the operation of the exhaust solenoid valve 36 are stopped. Therefore, no compressed air is supplied to the compressed air supply hole 40 at all. As a result, the diaphragm 24 returns to the return spring 2.
8, the valve body 37 is urged downward by the urging force.
Is pressed against the valve seat 27. Here, the return spring 28
Has a sufficiently strong force as compared with the return spring used in the conventional proportional solenoid type mass flow controller, so that the fluid is completely shut off by the valve body 17 and the valve seat 27. Become. At this time, the heat-sensitive coils R1 and R2 have detected that no fluid is flowing, and the control means 32 has confirmed that the flow rate is zero.

Next, a case where an input signal S, which is a command to flow a predetermined mass flow rate, to the control means 32 will be described. Since the current flow rate is zero, the control means 32 outputs the input signal S
The pulse conversion circuit 33 gives a drive pulse to the supply solenoid valve 35 and the exhaust solenoid valve 36 based on the difference. Supply solenoid valve 35 and exhaust solenoid valve 36
Performs an opening and closing operation according to a given pulse. The pulsed air pressure is supplied or discharged by the time opening and closing of the valve according to the pulse frequency, so that the air pressure of the compressed air supplied to the compressed air supply hole 40 can be finely adjusted easily and quickly. It is. Compressed air supply hole 4
The compressed air supplied from 0 pushes up the diaphragm 24 to separate the valve element 17 from the valve seat 27. Thereby, a fluid flows. Although the return spring 28 of this embodiment is a strong spring, since the diaphragm 24 is driven by compressed air, there is no problem even if the return spring 28 is strong.

Next, the operation of the mass flow meter will be described. Conduit 4
5, a fluid F flows in the direction indicated by the arrow. Each of the heat-sensitive coils R1 and R2 is connected to a constant temperature control circuit, and controls so that the temperatures of the heat-sensitive coils R1 and R2 are always equal and constant. That is, when the fluid F flows in the direction of the arrow in the conduit 45, the temperature of the heat-sensitive coil R1 wound on the upstream side of the conduit 45 is lowered because the fluid loses heat. In order to make it higher, the output voltage is higher than the output voltage when the fluid F is not flowing.

The temperature of the heat-sensitive coil R2 wound downstream of the conduit 45 is increased because the heat is applied by the fluid F heated by the heat-sensitive coil R1. To lower it, the output voltage will be lower than when the fluid F is not flowing. Therefore, the voltage output from the constant temperature control circuits is proportional to the amount of energy required to maintain the thermosensitive coils R1 and R2 at a constant temperature in each of the constant temperature control circuits. Here, the voltage difference is proportional to the mass flow rate of the fluid F, and the mass flow rate can be measured by measuring the voltage difference.

The measured mass flow is fed back to the control means 32, and the control means 32 supplies the supply solenoid valve 35 and the exhaust solenoid valve via the pulse conversion circuit 33 so that the difference from the input signal S is reduced. 36 is controlled. And
When the measured mass flow rate is smaller than the input signal S, the supply solenoid valve 35 performs an opening / closing operation in accordance with the pulse given from the pulse conversion means, and supplies compressed air acting on the diaphragm 24. Further, when the measured mass flow rate is larger than the input signal S, the exhaust solenoid valve 36 performs an opening / closing operation in accordance with the pulse given from the pulse conversion unit,
The compressed air acting on the diaphragm is exhausted. Solenoid valve 3 for supplying air pressure of compressed air acting on diaphragm 24
5 and the exhaust solenoid valve 36 are used for simultaneous control, so that the air pressure can be controlled with high responsiveness and the position of the valve element 17 can be controlled, so that an accurate flow rate can be obtained quickly.

Next, returning to FIG. 1, the wiring of the overall control system will be described. The controller 19, which is a control mechanism of the mass flow controller, can control four mass flow controllers at the same time. The controller 19 includes four lines of pressure sensors 12A, 12B, 12
C, 12D, four line shut-off valves 14A, 14
B, 14C, 14D, sensor units 16A, 16B, 16C, 16D, 4
Valve unit 17 of two-line mass flow controller
A, 17B, 17C, 17D, and four lines of shutoff valves 18A, 18B, 18C, 18D are respectively connected. The controller 19 is connected to a host computer 20 that controls the entire semiconductor manufacturing process.

Next, the operation of the mass flow controller system having the above configuration will be described. In this semiconductor process, four mass flow controllers are used in the same place, and they are put together to form a unit. Here, four mass flow controllers 15
Each of A, 15B, 15C, and 15D includes only a valve mechanism including a sensor unit 16 and a valve unit 17. As a control mechanism, a controller 19 as one control mechanism includes four mass flow controllers 15A, 15B, 15C, Fifteen
D is housed in a separate casing and attached to the unit. When controlling the four valve mechanisms, the controller 19 can perform sampling control at intervals of about 10 msec, which is sufficient as the sampling interval of the mass flow controller 15 currently used. The controller 19 as one control mechanism controls each valve mechanism by sequentially sampling the four valve mechanisms.

Since only one control mechanism is required as compared with the conventional mass flow controller, even if a high-performance cpu is used as the controller 19, the cost can be reduced. Further, even when the sensor mechanism 16 is clogged and the valve mechanism is replaced, there is no need to replace the controller 19, so that there is no waste. Furthermore, in the valve mechanism, if the valve section 17 and the sensor section 16 are separately housed in separate casings so that each can be replaced as a separate body, the type of the valve section 17 and
Since only the types of the sensor units 16 need to be prepared, the types of replacement parts to be stocked can be reduced.

As described above in detail, according to the mass flow control system of the present embodiment, the valve mechanism including the valve element, the valve seat, and the sensor section 16;
And a control mechanism for controlling a mass flow rate of the fluid by changing the position of the valve body by obtaining the output of the mass flow controller. 15A, 15B, 15C, 15D and 2
The above mass flow controllers 15A, 15B, 15
C and 15D, so that one controller 19 controls each valve mechanism by sequentially sampling the four valve mechanisms. Since only one control mechanism is required, cost can be reduced even if a high-performance cpu is used as the controller 19. Further, when the sensor mechanism 16 is clogged and the valve mechanism is replaced, there is no need to replace the controller 19, so that waste is eliminated. Further, in the valve mechanism,
If the valve section 17 and the sensor section 16 are separately housed in separate casings and can be replaced separately, the type of the valve section 17 and the type of the sensor section 16 can be replaced. Since it suffices to prepare them, the types of replacement parts to be stocked can be reduced.

It should be noted that the present invention is not limited to the above-described embodiment at all, and can be carried out as follows without departing from the spirit of the present invention. For example, in each of the above embodiments, the controller 19 controls four mass flow controllers, but it is also possible to control five or more mass flow controllers.

[0027]

According to the mass flow control system of the present invention, a valve mechanism including a valve element, a valve seat, and a flow rate sensor section is obtained by changing the position of the valve element by obtaining the output of the flow rate sensor section. In a mass flow control system using a mass flow controller including a control mechanism for controlling a mass flow rate of a fluid, two or more valve mechanisms that exist independently and one that controls the two or more valve mechanisms are provided.
Since one controller 19 controls each valve mechanism by sequentially sampling two or more valve mechanisms, the control mechanism has one controller 19 as compared with a conventional mass flow controller. Therefore, the cost can be reduced even if a high-performance cpu is used as the control mechanism. Further, even when the flow rate sensor section is clogged and the valve mechanism is replaced, there is no need to replace the control mechanism, so that there is no waste. Further, in the valve mechanism, if the valve section and the sensor section are separately housed in separate casings so that they can be replaced separately, the replacement parts include the type of the valve section and the type of the sensor section. Can be prepared, so that the types of replacement parts to be stocked can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a mass flow control system according to an embodiment of the present invention.

FIG. 2 is a drawing showing a configuration of a sensor unit 16 and a valve unit 17;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Regulator 12 Pressure sensor 14 Shutoff valve 15 Mass flow controller 16 Sensor part 17 Valve part 18 Shutoff valve 19 Controller 20 Host computer

Claims (2)

[Claims] A valve mechanism including a valve body, a valve seat, and a flow sensor; a control mechanism for controlling a mass flow rate of a fluid by obtaining an output of the flow sensor and changing a position of the valve body; A mass flow control system using a mass flow controller composed of two or more valve mechanism units that exist independently, and one control mechanism that controls the two or more valve mechanism units. Mass flow control system. 2. The mass flow control system according to claim 1, wherein the valve unit including the valve body and the valve seat, and the sensor unit are housed in separate casings, and the sensor unit is connected to the valve unit from the valve unit. A mass flow control system that can be separated and replaced.