JPH03230204A - Mass-flow controller - Google Patents

Abstract

PURPOSE:To enable accurate flow rate control with high accuracy in a high temperature state and to prevent gas from being liquefied by providing a temperature sensor which detects the temperature of a main body and a temperature correcting circuit which corrects the temperature. CONSTITUTION:This mass-flow controller is provided with a main body heating heater 5 which is embedded in the value main body 1a, the temperature sensor 6 which detects the temperature of valve main body 1a, a temperature control circuit 7 which controls a heater 5 for maintaining temperature set previously by the temperature sensor 6, and the temperature correcting circuit 11 which corrects the output of a flow rate sensor part 3 with ambient temperature. Therefore, the temperature control circuit 7 can hold the whole mass-flow controller at the previously set temperature and the temperature correcting circuit 11 can maintain certain constant temperature without decreasing the performance of stable flow rate control irrelevantly to variation in the ambient temperature. Consequently, the stable flow rate control over even gas which is easily liquefied at room temperature is performed without liquefying the gas.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mass flow controller used in a dry etching process, a CVD process, or the like in the manufacturing process of a semiconductor device 1.

[Conventional technology]

FIG. 3 is a block diagram showing an example of a conventional mass flow controller. Conventionally, two types of mass flow controllers have a large number of bypass paths 2 on the gas inflow side, through which the gas branches and flows, as shown in the figure, and a bypass path 2 is provided parallel to the bypass paths 2 on the outside. A valve body 1 has a control valve 4 that controls the flow rate of gas discharged from a flow rate sensor section 3 through a bypass path 2.
, a heating resistor 3a wound around the outside of the flow rate sensor section 3, which is a capillary tube made of stainless steel, and this heating resistor 3a form a bridge circuit, and the flow rate from the upstream side to the downstream side is generated by the gas flowing inside the flow rate sensor section 3. Bridge circuit 1 that generates an output proportional to the mass flow rate of the amount of heat transferred to the side
2, and an arithmetic circuit 8 that calculates the output of this bridge circuit 1.
and a comparison control circuit 9 that controls opening and closing of the control valve 4 by comparing the calculated output signal and the flow rate setting signal 10. Furthermore, as described above, by providing a bypass flow path in parallel with the flow rate sensor section 3 to separate the flow, a wide range of flow rate measurement ranges can be accommodated.

Furthermore, the output signal from the flow rate sensor section 3 is compared with a setting signal given from the outside by a comparison control circuit 9,
The valve opening degree of the control valve 4 is automatically controlled so that the difference is always zero.

[Problem to be solved by the invention]

Normally, various types of semiconductor gases are used in the manufacturing process of semiconductor integrated circuit devices, but in the dry etching process and CVD process, CCρ
4. BCl2.5iH2Cff12. A gas such as TE01, which has a low vapor pressure and is easily liquefied at room temperature, is used. Therefore, when using such a gas in the conventional mass flow controller described above, there is a drawback that accidents such as clogging due to gas liquefaction are likely to occur in the capillary tube of the flow sensor part or control valve inside the mass flow controller. . In addition, as a measure to prevent clogging of this mass flow controller, for example, wrapping a heater around the main body is used to raise the temperature, but conventional mass flow controllers can only be used at an environmental temperature of 50 degrees Celsius. There is a problem in that the flow rate control performance deteriorates due to the fact that the flow rate sensor section is affected by temperature fluctuations due to heating by the heater.

An object of the present invention is to eliminate such drawbacks and provide a mass flow controller that does not cause clogging caused by gas liquefaction.

[Means to solve the problem]

The mass flow controller of the present invention has a large number of gas introduction bypass paths and a flow rate sensor section which is a capillary tube into which the gas flows in at one end side, and a front gas bypass path and a flow rate sensor section at the other end side where the gas flows out from the flow rate sensor section. A mass flow controller comprising a main body having a control valve that controls the flow rate of gas, and a comparison control circuit that detects the output of the flow rate sensor section and controls opening/closing of the control valve. The present invention is characterized in that it includes a temperature sensor that detects the temperature of the main body, and a temperature correction circuit that corrects the output of the flow rate sensor section based on the temperature detected by the rice bran temperature sensor and the ambient temperature.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of a mass flow controller showing one embodiment of the present invention. In addition to the conventional mass flow controller, this mass flow controller includes a heater 5 embedded in the valve body 1a for heating the valve body 1a, a temperature sensor 6 for detecting the temperature of the valve body 1a, and a temperature set in advance by the temperature sensor 6. This is achieved by providing a temperature control circuit 7 that controls the heater 5 in order to maintain the flow rate at a constant temperature, and a temperature correction circuit 11 that corrects the output of the flow rate sensor 3 based on the ambient temperature.

Next, the operation of this mass flow controller will be explained.

First, gas passes through the bypass path 2 and the flow rate sensor section 3 as shown by the arrow. This flow rate sensor section 3 has two self-heating resistors wound around the outside of a stainless steel capillary tube, and is connected to a bridge circuit 12. The amount of heat transferred from the upstream side to the downstream side caused by the gas flowing in the capillary tube is measured as an output proportional to the mass flow rate. Since there is a limit to the flow rate flowing through this flow rate sensor section 3, by providing a bypass flow path 2 in parallel with the flow rate sensor and dividing the flow, a wide range of flow rate measurement ranges can be accommodated. Further, the output signal from the flow rate sensor unit is compared with a flow rate setting signal 10 given from the outside by a comparison control circuit 9, and the opening degree of the control valve 4 is automatically controlled so that the difference is always zero.

On the other hand, a heater 5 and a temperature sensor 6 are incorporated in the valve body 1a, and the entire mass flow controller can be maintained at a constant temperature set in advance by a temperature control circuit 7. Furthermore, with conventional mass flow controllers, the environmental temperature that can be used is up to about 50'C.
The flow rate sensor section 3 is easily affected by changes in ambient temperature, and if it is heated by a heater or the like, an error will occur in the output of the flow rate sensor section 3, resulting in a decrease in the performance of flow rate control. In other words, CC! 2
4. BCρ3,5iH2Cρ2. When using a gas that easily liquefies, such as TE01, clogging is likely to occur due to liquefaction, so great care must be taken in controlling the environmental temperature and pressure of the gas piping system.

However, in this mass flow controller, the temperature correction circuit 11 enables stable flow control regardless of changes in ambient temperature, so it is possible to maintain a certain high temperature without causing a drop in flow control performance. This makes it possible to perform stable flow rate control without liquefying even gases that tend to liquefy at room temperature.

FIG. 2 is a block diagram of a mass flow controller showing another embodiment of the present invention. As shown in the figure, this mass flow controller has the configuration of the above-described embodiment without the heater and temperature control circuit. In other words, it is applied when the surrounding environmental temperature is controlled by external equipment or the like. This is the case when this mass flow controller is used in an air conditioned room.

〔Effect of the invention〕

As explained above, the present invention provides a temperature sensor that detects the temperature of the main body and a temperature correction circuit that corrects it, so that flow rate control can be performed accurately and with high precision in a high temperature state. .5iHz CI!
It is possible to prevent the liquefaction of gases such as z, TE01, etc., and there is an effect that a mass flow controller that does not cause clogging due to liquefaction of the gas can be obtained.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a mass flow controller showing one embodiment of the present invention, Section 2 is a block diagram of a mass flow controller showing another embodiment of the invention, and Fig. 3 is a block diagram showing an example of a conventional mass flow controller. It is a diagram. 1.1a, lb... Valve body, 2... Bypass path, 3... Flow rate sensor section, 4... Control valve, 5... Heater, 6... Temperature sensor, 7... Temperature Control circuit, 8... Arithmetic circuit, 9... Comparison control circuit,
10...Flow rate setting signal, 11...Temperature correction circuit.

Claims (1)

[Claims] a control valve that has a large number of gas introduction bypass paths and a flow rate sensor section that is a capillary tube through which the gas flows in at one end side, and controls the flow rate of the gas flowing out from the bypass path and the flow rate sensor section at the other end side; and a comparison control circuit that detects the output of the flow rate sensor section and controls opening/closing of the control valve, the mass flow controller comprising: a temperature sensor that is embedded in the main body and detects the temperature of the main body; A mass flow controller comprising: a temperature correction circuit that corrects the output of the flow rate sensor section based on the temperature detected by the temperature sensor and the ambient temperature.