JPH04235611A - Mass flow controller - Google Patents

Abstract

PURPOSE:To early detect a trouble of a product and to prevent the occurrence of the trouble by comparing the output signal of a valve initial data circuit with the output of a flow rate control valve end displaying the result of the comparison. CONSTITUTION:The initial value data on the output signal applied to a flow rate control valve 4 under an optional level of pressure of the measured gas are previously inputted to 8 valve initial data circuit 10. When the measured gas flows to 8 sensor pipe 2, the thermal balanced states of the self-heating resistors 3a and 3b are lost and therefore a due output signal is outputted to an amplifier circuit 6 from a detector circuit 5. The output signal of the circuit 6 is sent to 8 flow rate display device end at the same time compared with 8 flow rate setting signal 8 by a comparison control circuit 7. The valve 4 is controlled based on the result of the comparison. The output signal of the circuit 7 is outputted to the valve 4 and at the same time compared with the output of the circuit 10 by 8 comparator 11. Then the difference between the output signal and the output is shown on a flow rate error display device 12.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass flow controller that adjusts the flow rate of gas, and more particularly to a mass flow controller that adjusts the flow rate of process gas in semiconductor manufacturing equipment.

0002

[Prior art] A conventional mass flow controller is shown in Fig. 3.
As shown in the block diagram of FIG. Amplification circuit 6 for amplifying the output signal of detection circuit 5
and a flow rate indicator 9 that displays the output signal of the amplifier circuit 6.
It is comprised of a comparison control circuit 7 that compares the output signal of the amplifier circuit 6 and the flow rate setting signal 8 and controls the flow rate adjustment valve 4.

Next, the operation will be explained. The gas entering from the IN side of the mass flow controller is divided into the gas flowing through the sensor pipe 2 and the gas flowing through the bypass section 1, and then joins again, passes through the flow rate adjustment valve 4, and exits from the OUT side of the mass flow controller. come. At this time, the self-heating resistors 3a, 3b that have generated heat in advance are cooled by the gas to be measured.
After the detection circuit 5 detects a change in the resistance value of b, the output signal of the amplifier circuit 6 is compared with the flow rate setting signal 8, and the flow rate adjustment valve 4 is controlled, thereby making it possible to adjust the flow rate. Since the output generated in the detection circuit 5 is proportional to the mass flow rate, the mass flow rate can be adjusted accurately.

0004

Problems to be Solved by the Invention In the circuit configuration of this conventional mass flow controller, in particular, Bcl3, cl2
When using a highly corrosive gas such as SiH4 or a gas that easily clogs, such as SiH4, when using it for a long period of time, or when a leak occurs in the piping system, the sensor pipe 2 or bypass section 1 may become clogged. , sensor tube 2 and bypass section 1
The diversion ratio with the current flow will collapse. If a product such as a gas to be measured adheres to the inside of the sensor tube 2, the flow rate in the sensor tube 2 cannot be maintained, so the flow rate adjustment valve 4 moves in the direction of opening, so that the actual flow rate is greater than the set flow rate. Further, the display on the flow rate indicator 9 at this time is the same as the set flow rate because it detects the flow rate only in the sensor tube 2, and no abnormality can be detected. In this way, even if the splitting ratio is disrupted due to adhesion of products or the like in the sensor tube 2 or the bypass section 1 and the actual flow rate of the gas to be measured changes, no abnormality will be seen on the flow rate indicator 9.
If used as is, it would cause product abnormalities and troubles.

[0005]

[Means for Solving the Problems] The mass flow controller of the present invention includes a valve initial data circuit that inputs flow rate setting data and outputs an initially set output signal of the valve;
It is comprised of a comparison circuit that compares the output signal of the valve initial data circuit and the output signal to the flow rate adjustment valve, and a flow rate deviation indicator that displays the comparison result.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings. FIG. 1 is a block diagram of a mass flow controller according to a first embodiment of the present invention. The gas to be measured that has entered the mass flow controller is first divided into the sensor tube 2 and the bypass section 1 . When the gas to be measured flows through the sensor tube 2, the thermal equilibrium state of the self-heating resistors 3a and 3b is disrupted, and an output signal corresponding to this is outputted from the detection circuit 5 to the amplifier circuit 6. The output signal of the amplifier circuit 6 is sent to a flow rate indicator 9, while being compared with a flow rate setting signal 8 in a comparison control circuit 7, and the flow rate regulating valve 4 is controlled accordingly. The output signal from the comparison control circuit 7 is output to the flow rate adjustment valve 4, and is compared with the output from the valve initial data circuit 10 in the comparison circuit 11, and the amount of deviation is displayed on the flow rate deviation indicator 12. Is displayed. Further, data of the initial value (normal state) of the output signal to the flow rate adjustment valve 4 at an arbitrary pressure of the gas to be measured is inputted into the valve initial data circuit 10 in advance. In this way, conventionally, even if the actual flow rate of the gas to be measured differs from the set flow rate due to a change in the split flow ratio between the sensor tube 2 and the bypass section 1, no abnormality is recognized on the flow rate indicator. Since the amount of deviation in the output signal to the flow rate adjustment valve 4 is displayed under a certain arbitrary pressure, early detection is possible and troubles to the product can be prevented.

Next, a second embodiment will be explained. In the block diagram of FIG. 2, I of the mass flow controller
A pressure sensor 13 is attached to the N side. The output signal from the pressure sensor 13 is compared with the output signal of the comparison control circuit 7 and the output signal of the valve initial data circuit 10 in the comparison circuit 11, and the result is displayed on the flow rate deviation indicator 12. In this embodiment, even if the pressure of the gas to be measured fluctuates, the amount of deviation from the initial value (normal) can be accurately displayed.

[0008]

As explained above, according to the present invention, even when the quantity ratio of the mass flow controller changes and the actual flow rate of the gas to be measured changes, the initial value of the output signal to the flow rate adjustment valve (normal ), it is possible to detect troubles in the mass flow controller early and prevent product troubles, which is highly effective in improving yields and preventing product troubles.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a block diagram of a second embodiment of the present invention.

FIG. 3 is a block diagram of a conventional mass flow controller.

[Explanation of symbols]

1 Bypass section 2 Sensor tube 3a, 3b Self-heating resistor 4 Flow rate adjustment valve 5 Detection circuit 6 Amplifier circuit 7 Comparison control circuit 8 Flow rate setting signal 9 Flow rate indicator 10 Valve initial data circuit 11 Comparison circuit 12 Flow rate deviation indicator 13 Pressure sensor

Claims (1)

[Claims] 1. A valve initial data circuit that stores initial data of an output signal to a flow rate adjustment valve corresponding to a flow rate setting signal, and an output signal of the valve initial data circuit and an output signal to the flow rate adjustment valve. A comparison circuit for comparison,
A mass flow controller comprising a flow rate deviation indicator that displays the comparison results.