JPH0384421A - Flow rate detecting method - Google Patents

Abstract

PURPOSE:To detect a flow rate without bringing a sensor into contact with 1st fluid and to prevent malfunction due to the sticking of a foreign matter and to improve the durability by injecting a specific amount of 2nd fluid into the front surface of the sensor which measures the flow rate of the 1st fluid. CONSTITUTION:An injection pipe 17 for purge PG as the 2nd fluid is provided in front of the sensor 15 fitted in piping 13, and a controller 18 controls its injection amount. When the flow rate of the 1st fluid gas G which contains resist mist and flows in the piping 13 is measured, the gas PG whose supply amount is controlled is supplied to the front of the sensor 15 to cover the sensor 15, which can measures the flow rate of the gas G and gas PG without contacting the gas PG. Then measured values are inputted to a controller 20 and a dumper 24 controls the flow rate of the gas G. Consequently, the malfunction due to the sticking of foreign matter in the gas G is precluded and the durability of the sensor can be improved.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for detecting the flow rate of fluid flowing in a pipe.

[Prior Art and Problems to be Solved by the Invention] Conventionally, in the semiconductor manufacturing process, in order to obtain a desired pattern of a thin film, a photosensitive resist is coated on a thin film formed on a wafer, and then the desired pattern is applied. After exposure, development is performed using a mask with a metal thin film created in the above. In the coating process of applying this resist, it is necessary to form a uniform coating film in order to form a high quality semiconductor. Therefore, a coating device or a developing device drips a certain amount of highly viscous resist or developer onto the semiconductor wafer, which is the object to be processed, and coats the semiconductor wafer by rotating it at high speed in a cup that surrounds the chuck. There are spin coaters, spin developers, etc.

In such spin coaters and spin developers, processing liquids such as resist and developer are stretched by high-speed rotation, but the excess processing liquid is blown to the cup wall, reflected, and redirected onto the semiconductor wafer as the object to be processed. In order to prevent the liquid from being returned and contaminated, it is sucked in by a drain or the like from the bottom of the cup and discharged along with the air. This processing liquid is in the form of a mist, and in order to control the air containing the mist to be exhausted from the cup in a predetermined amount, a filter 2 is installed in the exhaust pipe 1 as shown in Fig. 4. established,
After removing the mist, the control device 4 opens and closes the flow rate control means 5 based on the detected value of the flow rate sensor 3, thereby controlling the exhaust amount.

However, at this time, the removal of the mist by the filter 2 is not complete, and the mist adheres to the sensing part of the sensor 3.
There have been drawbacks such as solidification of the solvent, resist solution, or developer, which may cause detection errors, and the life of the resensor, which cannot be detected, is significantly shortened.

The flow rate detection method of the present invention has been made in order to eliminate the above-mentioned drawbacks, and the purpose of the present invention is to prevent the mist of processing liquid from adhering to the sensor, and to easily improve the durability of the sensor. The present invention provides a flow rate detection method that allows the flow rate to be measured.

[Means for Solving the Problems] In order to achieve the above object, 1 the flow rate detection method of the present invention provides a method for detecting a flow rate of a first fluid flowing in a pipe with a sensor installed in the pipe. A predetermined amount of the second fluid is injected into the front surface, and the sensor detects the flow rate of the first fluid without contacting the first fluid.

[Operation] The present invention is a device that uses a sensor to detect the flow rate of a fluid containing foreign matter or a fluid that corrodes the sensor flowing through piping, and operates a flow rate control means based on the detected value, in which the flow rate of the detected object is measured. A predetermined amount of another purge fluid that does not contain foreign matter is injected in front of the sensor to be detected. It is designed to know the flow rate of material. Therefore, it is possible to prevent malfunctions due to erroneous detection caused by foreign matter contained in the object to be detected adhering to the sensor, and to improve the durability of the sensor.

[Example] An example in which the flow rate detection method of the present invention is applied to a coater used in a resist coating process of semiconductor manufacturing will be described with reference to the drawings.

The coater shown in FIG. 1 is provided with an upper disc-shaped chuck 7 which is fixed to the rotating shaft of a motor 6 on which a semiconductor wafer W is placed and fixed by vacuum suction or the like. A discharge nozzle 8 for dropping liquid onto the semiconductor wafer W is provided. If dispensing from the dispensing nozzle 8 is not performed for a predetermined period of time due to a break in the loft, etc., the resist liquid at the tip of the dispensing nozzle 8 may harden due to contact with air for a long period of time, so dummy dispensing is performed. Therefore, in order to retract the discharge nozzle 8 from above the chuck 7 to a position outside the chuck 7, it is movable by the scanner 9.

A resist supply system 10 which is a resist supplying device to which this discharge nozzle 8 is connected includes a pump that supplies a desired fixed amount of resist from a resist storage container (not shown), and a pump that draws the resist back into the discharge nozzle 8 after being discharged from the discharge nozzle 8. ,
A suckback valve or the like is provided to prevent the resist from dripping or solidifying. Further, a cup 11 is provided surrounding the chuck 7 as a processing container to prevent the resist from scattering outside the apparatus during resist application. The cup 11 is movable up and down, and is lowered from the illustrated position when loading and unloading the semiconductor wafer W.

The chuck 7 is exposed to facilitate loading and unloading. cup 11
A drain box 12 is provided at the bottom of the vacuum chamber 't1.
(not shown). As shown in FIG. 2, the exhaust pipe 13 is provided with a trap 14 for removing the resist liquid mist in the exhaust gas G, which is the first fluid.
is provided, and the flow rate of the exhaust gas G that has passed through the trap 14 is measured by a sensor 15. In front of the sensor 15, a purge gas injection pipe 17 connected to a purge gas supply system 16 of a supply body for purge gas PG, which is a second fluid, which is a feature of the present invention, is arranged, and a purge gas controller 18 automatically closes a valve 19. The purge gas P is
It is provided so that the amount of G to be injected is controlled and injected around the sensor 15.

A hot wire current meter or the like is used as the sensor 15, and the output from the sensor 15 is input to a mass flow controller 20 to adjust the flow rate. The sensor 15 is, for example, a capillary tube 22 with two self-heating resistors 23 wound around it, as shown in the configuration diagram of FIG. Ru. The mass flow controller 20 is provided with a bridge circuit 24, and when the measurement gas flows into the capillary tube 22 of the sensor, the balance of the bridge circuit 24 is lost due to the movement of heat, and an electrical signal proportional to the mass flow rate is output. This electric signal is amplified by an amplifier circuit 25, and a correction circuit 27 regarding the purge gas flow rate detects the flow rate of exhaust gas. Furthermore, a comparison control circuit 28 is provided to compare the output voltage of the detected value with a preset voltage, and the damper 21 is controlled so that the difference between the two voltages becomes O, and the flow rate is detected by feedback control. It has become. in this way,
The mass flow controller 20 adjusts the component amount of the purge gas PG, determines the actual flow rate of the exhaust gas G, operates the damper 21 according to that value, and opens and closes it! The flow rate of the exhaust gas G is controlled by adjusting the flow rate of the exhaust gas G. Also, sensor 1
As the sensor 5, a capacitance type proximity sensor or the like which detects by utilizing the dielectric coefficient of the object to be detected is also suitably used. If the transistors and oscillators incorporated in the capacitive proximity sensor are made of silicon, they can be applied to a wide range of temperature changes.

The flow rate detection method of the present invention will be explained in the coater configured as above.

The semiconductor wafer W is transferred to the chuck 7 by a transport mechanism (not shown).
When placed on top and fixed by suction, the cup 11 rises as shown in FIG. 1, and a certain amount of resist is dropped from the resist supply system 10 onto the center of the semiconductor wafer W from the discharge nozzle 8. The chuck 7 rotates at a rate of, for example, 4000 times/min as the motor 6 rotates, and the resist is formed on the semiconductor wafer W.
The area is extended to the periphery of the area. Then, the excess resist scatters from the semiconductor wafer and forms a mist that hits the wall surface of the cup 11. However, at this time, the exhaust pipe 13 connected to the vacuum device is sucked together with air, preventing it from returning onto the semiconductor wafer W again. The resist mist in the exhaust gas G sucked into the exhaust pipe 13 is trapped in a mesh-like trap 1.
Most of the resist mist is collected by the exhaust gas G, but a small amount of the resist mist passes through the trap 14 and remains in the exhaust gas G. Here, a purge gas PG such as cleaned air or N2 is supplied from a purge gas supply system 16 by a purge gas controller 18 controlling a valve 19 to control the supply amount to the sensor 1.
It is supplied to the front of 5. The supply amount of purge gas PG is determined by the flow rate of exhaust gas G, exhaust pipe 13 and purge gas injection pipe 1.
For example, the inner diameter of the exhaust pipe 13 is 50 to 60+n+, the inner diameter of the purge gas injection pipe 17 is 4 to 61IIll, and the flow rate of the exhaust gas G is approximately 1.
rrr/win, then IQ/l1in is suitable. In this way, the purge gas PG covers and protects the sensor 15, and the sensor 15 measures the flow rates of the exhaust gas G and purge gas PG without coming into contact with the exhaust gas G, and inputs the flow rates to the mass flow controller 20. operates the damper 21 to feedback control the flow rate of the exhaust gas G.

Here, in order to obtain the actual flow rate of the exhaust gas G, which is obtained by subtracting the supply amount of the purge gas PG from the measured value of the sensor 15, a predetermined relationship is used. If the sensor 15 is a pressure sensor, if the pressure P0 that acts on the sensor 15 when a constant amount of purge gas PG is supplied is determined in advance, the pressure P0 applied by the flow rate U of the exhaust gas G can be determined in advance. When ' is P'=f(U), if the pressure P is measured by the sensor 15, p = p, +p' holds, that is, p' = p - p.

Then, the flow rate of exhaust gas G can be determined.

In the above explanation, the purge gas PG is constantly injected, and the sensor 15
However, if the sensor 15 measures the flow rate of the exhaust gas G intermittently, the supply of the purge gas PG is interrupted when the sensor 15 measures,
The purge gas PG may be supplied outside the measurement time of the sensor 15 to cover the sensor 15. In this case, the measured value of the sensor 15 becomes the actual flow rate of the exhaust gas G.

Adjustment means are no longer necessary and are simpler.

The above description is an example of the present invention, and the present invention is not limited thereto, and can be applied to other semiconductor manufacturing equipment such as a developer, and is not limited to semiconductor manufacturing.
It can be suitably applied to measuring the flow rate of fluids such as those containing foreign substances, corrosive or reactive gases, liquids, etc.

[Effects of the Invention] As is clear from the above description, according to the flow rate detection method of the present invention, resist,
Gases containing solvents, etc., and corrosive properties.

Since there is no direct contact with reactive fluids, there is no foreign matter adhering to the sensor, no erroneous measurements, etc., greatly extending the life of the sensor, and providing durable and reliable flow rate detection. .

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment to which the flow rate detection method of the present invention is applied, FIG. 2 is a diagram showing the main parts of the embodiment shown in FIG. 1, and FIG. FIG. 4 is a diagram showing a conventional example. 13... Exhaust pipe (piping) 15... Sensor 20... Mass flow controller 21...
···damper

Claims (1)

[Claims] When detecting the flow rate of the first fluid flowing in the pipe with a sensor installed in the pipe, a predetermined amount of the second fluid is injected in front of the sensor, and the sensor comes into contact with the first fluid. A flow rate detection method characterized in that the flow rate of the first fluid is detected without detecting the flow rate of the first fluid.