WO2013143116A1

WO2013143116A1 - Flow control system and method thereof

Info

Publication number: WO2013143116A1
Application number: PCT/CN2012/073302
Authority: WO
Inventors: Jian Wang; Yu Zhao; Liangzhi Xie; Xiaoyan Zhang; Shena JIA; Hui Wang
Original assignee: Acm Research (Shanghai) Inc.
Priority date: 2012-03-30
Filing date: 2012-03-30
Publication date: 2013-10-03
Also published as: KR20140140623A

Abstract

A flow control system and method thereof are disclosed. The flow control system includes a control valve for liquid flowing through, a pressure sensor measuring a pressure of the liquid flowing through the control valve and outputting a measuring signal, a controller receiving the measuring signal from the pressure sensor and outputting a corresponding electric current signal, an I/P converter receiving the electric current signal from the controller and outputting compressed air with corresponding pressure to the control valve to regulate the pressure of the liquid in the control valve, a flow switch measuring a flow rate of the liquid flowing into a chamber, and a needle valve regulating the flow rate to a target flow rate. The control valve, the pressure sensor, the I/P converter and the controller constitute a PID closed loop control system to provide a precise and stable liquid supply.

Description

FLOW CONTROL SYSTEM AND METHOD THEREOF

FIELD OF THE INVENTION

[0001] The present invention generally relates to a liquid supply system, and more particularly to a flow control system and method thereof capable of controlling the liquid supply precisely and stably during a semiconductor device fabrication process.

BACKGROUND

[0002] During a semiconductor device fabrication process, as known to all, a wafer is easy to be contaminated. Micro contaminations such as surface particles, polymer residues, metallic impurities and chemical oxides adhering to a surface of the wafer will bring an increasing detrimental impact on the property of the semiconductor device as the semiconductor device continues to shrink. Almost every step in the semiconductor device fabrication process is a potential source of the contaminations. Therefore, cleaning the surface of the wafer is very essential to obtain a high quality semiconductor device. At present, there are several kinds of cleaning methods with the semiconductor technology development. Thereinto, a wet cleaning method is widely used for removing the contaminations from the surface of the wafer, which generally utilizes liquid such as ultrapure water and/or various kinds of chemical to clean the surface of the wafer. The liquid is supplied to cleaning chambers where the wafer is cleaned.

[0003] In order to ensure the cleaning effect and the high quality of the semiconductor device, flow of the liquid supplied to the cleaning chambers should be controlled precisely and stably. A conventional flow control system includes several control valves. Each liquid transport channel which connects one of the cleaning chambers has one control valve to supply the stable and precise liquid flow to the cleaning chamber. Although the conventional flow control system can provide the anticipant liquid flow to the cleaning chamber, the cost is very high because the control valve is expensive. Besides, lots of the control valves occupy too much space, which increases the difficulty of installing other devices in the flow control system.

[0004] Hence, more extraordinary efforts will be made to reduce the cost and simplify the structure of the flow control system.

SUMMARY

[0005] In accordance with one aspect of an embodiment of the present invention, a flow control system is provided. The flow control system includes a control valve for liquid flowing through, a pressure sensor measuring a pressure of the liquid flowing through the control valve and outputting a measuring signal, a controller receiving the measuring signal from the pressure sensor and outputting a corresponding electric current signal, an I/P converter receiving the electric current signal from the controller and outputting compressed air with corresponding pressure to the control valve to regulate the pressure of the liquid in the control valve, a flow switch measuring a flow rate of the liquid flowing into a chamber, and a needle valve regulating the flow rate to a target flow rate.

[0006] In accordance with one aspect of another embodiment of the present invention, a flow control system is provided. The flow control system includes a control valve for liquid flowing through, a pressure sensor measuring a pressure of the liquid flowing through the control valve and outputting a measuring signal, a controller receiving the measuring signal from the pressure sensor and outputting a corresponding voltage signal, a U/P converter receiving the voltage signal from the controller and outputting compressed air with corresponding pressure to the control valve to regulate the pressure of the liquid in the control valve, a flow switch, measuring a flow rate of the liquid flowing into a chamber, and a needle valve, regulating the flow rate to a target flow rate.

[0007] In accordance with another aspect of an embodiment of the present invention, a flow control method is provided. The flow control method includes the following control procedures: constituting a PID closed loop control system with a control valve, a pressure sensor, an I/P converter and a controller; measuring a pressure of the liquid flowing through the control valve and outputting a measuring signal by the pressure sensor; receiving the measuring signal from the pressure sensor and outputting a corresponding electric current signal by the controller; receiving the electric current signal from the controller and outputting compressed air with corresponding pressure to the control valve to regulate the pressure of the liquid in the control valve by the I/P converter; measuring a flow rate of the liquid flowing into a chamber by a flow switch; and regulating the flow rate to a target flow rate by a needle valve.

[0008] In accordance with another aspect of another embodiment of the present invention, a flow control method is provided. The flow control method includes the following control procedures: constituting a PID closed loop control system with a control valve, a pressure sensor, a U/P converter and a controller; measuring a pressure of the liquid flowing through the control valve and outputting a measuring signal by the pressure sensor; receiving the measuring signal from the pressure sensor and outputting a corresponding voltage signal by the controller; receiving the voltage signal from the controller and outputting compressed air with corresponding pressure to the control valve to regulate the pressure of the liquid in the control valve by the U/P converter; measuring a flow rate of the liquid flowing into a chamber by a flow switch; and regulating the flow rate to a target flow rate by a needle valve.

[0009] As described above, the flow control system and method thereof provide a precise and stable liquid supply by using the PID closed loop control system. Even if the upstream liquid supply is unstable, the PID closed loop control system is able to self-regulate and provide the precise and stable liquid supply. According to different requirements of the process, the liquid flowing through the control valve and the pressure sensor can be divided into several distributed branches, and each branch has one flow switch, one needle valve and one chamber. When one branch is open or close, the flow rate of the liquid in other branches will not be influenced, because the PID closed loop control system can self-regulate and give the precise correction to let the flow control system remain the target liquid pressure and target liquid flow rate in each branch. Take a flow control system containing three branches for example, the flow control system employs one control valve, one pressure sensor, one I/P converter or one U/P converter, one controller, three needle valves and three flow switches to provide a precise and stable liquid supply. In contrast, a conventional flow control system should be made up of three control valves, three pressure sensors, three I/P converters or three U/P converters, three controllers and three flow meters. Thus, the present invention saves two control valves, two pressure sensors, two I/P converters or two U/P converters and two controllers. Also the flow switch is cheaper than the flow meter, and the overall system cost is cut down. In short, the cost of the flow control system is greatly reduced and the structure of the flow control system is simplified.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention will be apparent to those skilled in the art by reading the following description of preferred embodiments thereof, with reference to the attached drawings, in which:

[0011] FIG. 1 is a block diagram of a first embodiment of a flow control system of the present invention;

[0012] FIG. 2 is a block diagram of another embodiment of the flow control system of the present invention; and

[0013] FIG. 3 is a flow chart showing control procedures of the flow control system related to the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0014] Referring to FIG. 1 illustrating a first embodiment of a flow control system in accordance with the present invention, the flow control system includes a control valve 10, a pressure sensor 20, a controller 40 and an I/P converter 30, all of which constitute a PID closed loop control system. The pressure sensor 20 is used for measuring a pressure of liquid flowing through the control valve 10 and outputting a pressure electrical signal. The controller 40 receives the pressure electrical signal from the pressure sensor 20 and outputs a corresponding electric current signal to the I/P converter 30. The I/P converter 30 receives the electric current signal and outputs compressed air with corresponding pressure to the control valve 10 to regulate the pressure of the liquid in the control valve 10. The pressure of the liquid flowing through the control valve 10 and the pressure sensor 20 is capable of maintaining a set value by the self-regulation of the PID closed loop control system.

[0015] Alternatively, as illustrated in FIG. 2, the I/P converter 30 is replaced by a U/P converter 30', and accordingly, the controller 40 receives a pressure electrical signal from the pressure sensor 20 measuring a pressure of the liquid flowing through the control valve 10 and outputs a corresponding voltage signal to the U/P converter 30'. The U/P converter 30' receives the voltage signal from the controller 40 and outputs compressed air with corresponding pressure to the control valve 10 to regulate the pressure of the liquid in the control valve 10. The pressure of the liquid flowing through the control valve 10 and the pressure sensor 20 is capable of maintaining a set value by the self-regulation of a PID closed loop control system constituted by the control valve 10, the pressure sensor 20, the controller 40 and the U/P converter 30'.

[0016] Please continue to refer to FIG. 1 and FIG. 2. The liquid flowing through the control valve 10 and the pressure sensor 20 can be divided into several branches according to different requirements of the process. For example, in the preferred embodiments, the liquid is divided into three branches. Each branch includes a needle valve 50, a flow switch 60 and a chamber 70 where a wafer is cleaned. The liquid of each branch flows through the needle valve 50 and the flow switch 60 and then flows into the chamber 70 for cleaning the wafer. The flow switch 60 is used for measuring a flow rate of the liquid in each branch. The needle valve 50 can be a kind of manually operated valve and used for regulating the flow rate of the liquid in each branch based on the flow rate measured by the flow switch 60 until the flow rate is the desirous flow rate. Preferably, each branch further includes a pressure valve 80 for permitting or preventing the liquid flowing into the chamber 70.

[0017] Taking the first embodiment of the flow control system for example, the working mechanism of the flow control system is described herein. The pressure sensor 20 measures a pressure of the liquid flowing through the control valve 10 and transmits the measuring signal to the controller 40. The controller 40 receives the measuring signal and compares with a preset target liquid pressure and then outputs a corresponding electric current signal to the I/P converter 30 based on the comparison result. The I/P converter 30 receives the electric current signal from the controller 40 and outputs compressed air with corresponding pressure to the control valve 10 to regulate the pressure of the liquid in the control valve 10. The PID closed loop control system self-regulates until the liquid pressure in the control valve 10 is the same as the preset target liquid pressure. By regulating the needle valve 50 of each branch, the desirous flow rate of the liquid in each branch is obtained.

[0018] With reference to FIG. 3, taking the first embodiment for example, a flow control method is exemplified and includes following control procedures.

[0019] In SI step, set a target liquid pressure of the control valve 10, and the controller 40 generates and sends a corresponding electric current signal to the I/P converter 30.

[0020] In S2 step, the I/P converter 30 receives the electric current signal and outputs corresponding compressed air to the control valve 10.

[0021] In S3 step, the control valve 10 is driven by the compressed air to produce a current liquid pressure in the control valve 10.

[0022] In S4 step, the pressure sensor 20 measures the current liquid pressure of the control valve 10 and transmits the measuring signal to the controller 40. The controller 40 receives the measuring signal and compares the current liquid pressure with the target liquid pressure. If Pc=Pt, jump to S5 step. If Pc>Pt, the controller 40 outputs a smaller electric current signal to the I/P converter 30 to command the I/P converter 30 decreasing the pressure of the compressed air provided to the control valve 10, and then jump to the S2 step. If Pc<Pt, the controller 40 outputs a larger electric current signal to the I/P converter 30 to command the I/P converter 30 increasing the pressure of the compressed air provided to the control valve 10, and then jump to the S2 step. Wherein, the Pc indicates the current liquid pressure in the control valve 10, and the Pt indicates the target liquid pressure in the control valve 10.

[0023] In S5 step, compare current branch flow rate with target flow rate. If Fc=Ft, the regulation of the liquid pressure and the liquid flow rate is accomplished and the system will maintain. If Fc>Ft, manually turn down the needle valve 50 to decrease the flow rate of the liquid in the branch, and in the same time the liquid pressure in the control valve 10 rises, which results in Pc>Pt, and then jump to the S4 step. If Fc<Ft, manually turn up the needle valve 50 to increase the flow rate of the liquid in the branch, and in the same time the liquid pressure in the control valve 10 drops, which results in Pc<Pt, and then jump to the S4 step. Wherein, the Fc indicates the current flow rate of the liquid in each branch, and the Ft indicates the target flow rate of the liquid in each branch.

[0024] As described above, the flow control system and method thereof provide a precise and stable liquid supply by using the PID closed loop control system. Even if the upstream liquid supply is unstable, the PID closed loop control system is able to self-regulate and provide the precise and stable liquid supply. In related to the several distributed branches, when one pressure valve 80 is open or close, the flow rate of the liquid in other branches will not be influenced, because the PID closed loop control system can self-regulate and give the precise correction to let the flow control system remain the target liquid pressure and target liquid flow rate in each branch.

[0025] Meanwhile, the flow control system and method thereof just utilize one control valve 10, one pressure sensor 20, one I/P converter 30 or U/P converter 30', and one controller 40, all of which constitute the PID closed loop control system to regulate the liquid pressure in the control valve 10. Each branch of the system has one needle valve 50 and one flow switch 60 to regulate the flow rate of the liquid in each branch. Take a flow control system containing three branches for example, the flow control system employs one control valve 10, one pressure sensor 20, one I/P converter 30 or one U/P converter 30', one controller 40, three needle valves 50 and three flow switches 60 to provide a precise and stable liquid supply. In contrast, a conventional flow control system should be made up of three control valves 10, three pressure sensors 20, three I/P converters 30 or three U/P converters 30', three controllers 40 and three flow meters. Thus, the present invention saves two control valves 10, two pressure sensors 20, two I/P converters 30 or two U/P converters 30' and two controllers 40. Also the flow switch 60 is cheaper than the flow meter and the overall system cost is cut down. In short, the cost of the flow control system is greatly reduced and the structure of the flow control system is simplified.

[0026] The foregoing description of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. Such modifications and variations that may be apparent to those skilled in the art are intended to be included within the scope of this invention as defined by the accompanying claims.

Claims

What is claimed is:

1. A flow control system, comprising:

a control valve, for liquid flowing through;

a pressure sensor, measuring a pressure of the liquid flowing through the control valve and outputting a measuring signal;

a controller, receiving the measuring signal from the pressure sensor and outputting a corresponding electric current signal;

an I/P converter, receiving the electric current signal from the controller and outputting compressed air with corresponding pressure to the control valve to regulate the pressure of the liquid in the control valve;

a flow switch, measuring a flow rate of the liquid flowing into a chamber; and a needle valve, regulating the flow rate to a target flow rate.

2. The flow control system as claimed in claim 1, wherein the liquid flowing through the control valve and the pressure sensor is divided into several branches, each branch has one flow switch, one needle valve and one chamber.

3. The flow control system as claimed in claim 2, wherein each branch further includes a pressure valve for permitting or preventing the liquid flowing into the chamber.

4. The flow control system as claimed in claim 1, wherein the control valve, the pressure sensor, the I/P converter and the controller constitute a PID closed loop control system.

5. A flow control system, comprising:

a control valve, for liquid flowing through; a pressure sensor, measuring a pressure of the liquid flowing through the control valve and outputting a measuring signal;

a controller, receiving the measuring signal from the pressure sensor and outputting a corresponding voltage signal;

a U/P converter, receiving the voltage signal from the controller and outputting compressed air with corresponding pressure to the control valve to regulate the pressure of the liquid in the control valve;

6. The flow control system as claimed in claim 5, wherein the control valve, the pressure sensor, the U/P converter and the controller constitute a PID closed loop control system.

7. A flow control method, comprising:

constituting a PID closed loop control system with a control valve, a pressure sensor, an I/P converter and a controller;

measuring a pressure of the liquid flowing through the control valve and outputting a measuring signal by the pressure sensor;

receiving the measuring signal from the pressure sensor and outputting a corresponding electric current signal by the controller;

receiving the electric current signal from the controller and outputting compressed air with corresponding pressure to the control valve to regulate the pressure of the liquid in the control valve by the I/P converter;

measuring a flow rate of the liquid flowing into a chamber by a flow switch; and

regulating the flow rate to a target flow rate by a needle valve.

8. The flow control method as claimed in claim 7, further comprising dividing the liquid flowing through the control valve and the pressure sensor into several branches, each branch having one flow switch, one needle valve and one chamber.

9. The flow control method as claimed in claim 8, further comprising permitting or preventing the liquid flowing into the chamber for each branch by a pressure valve.

10. A flow control method, comprising:

constituting a PID closed loop control system with a control valve, a pressure sensor, a U/P converter and a controller;

receiving the measuring signal from the pressure sensor and outputting a corresponding voltage signal by the controller;

receiving the voltage signal from the controller and outputting compressed air with corresponding pressure to the control valve to regulate the pressure of the liquid in the control valve by the U/P converter;

regulating the flow rate to a target flow rate by a needle valve.