Patent Application
20050147530
This application claims the priority of Korean Patent Application No. 2003-58250, filed on Aug. 22, 2003 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of Invention
The present invention relates to a method and a detector for identifying the effective lifetime of an absorbent material in a gas scrubber, and to a gas scrubber including the detector, and more particularly, to a method and a detector for identifying the effective lifetime of the absorbent material to purify a harmful exhaust gas generated in a semiconductor manufacturing process, and to the gas scrubber including the detector.
2. Description of the Related Art
Gas generated during a semiconductor manufacturing process contains flammable and/or corrosive components, which make the gas very harmful to the human body and the environment. Therefore, the gas should be treated and made chemically safe before exhausting it to the atmosphere.
Process gases used in the semiconductor manufacturing process, such as SiH4, NH3, and AsH3 are flammable, explosive, and very toxic. However, a significant amount of these harmful gases are exhausted from a process chamber without reaction during the semiconductor manufacturing process. Therefore, these gases should be treated for safety purposes before discharging them into the atmosphere. A gas scrubber performs a cleaning function for these gases.
Since the process gases remaining in the chamber after finishing the semiconductor manufacturing process, and the cleaning gas used for cleaning the residual powder in the chamber, are harmful acidic gases, the harmful components in these gases should be removed before discharging them into the air from a gas scrubber. Examples of the cleaning gases include NF3 and HF.
The gas scrubber is a device for treating an exhaust gas generated in the semiconductor manufacturing process. Conventionally, the gas scrubber, depending on the gas treatment method, is classified into three types as follows: a wet type gas scrubber, a combustion type gas scrubber, and an absorption type gas scrubber.
The wet type gas scrubber neutralizes the exhaust gas using a washing liquid and then absorbs the treated gas. The wet type gas scrubber is suitable for treating a large volume gas, but has a disadvantage of incomplete treatment of insoluble gases, and requires an extra cost for a wastewater treatment.
The combustion type gas scrubber burns and decomposes the exhaust gas at a high temperature. It also has the advantage of being able to handle a large capacity. However, it also requires an extra cost for treating any harmful by-products.
The absorption type gas scrubber uses an absorbent material to remove harmful components by absorption. In the absorption type gas scrubber, the absorbent material is filled in a canister that is disposed in the gas scrubber to remove harmful gas. The absorbent material purifies the harmful gas used in the semiconductor manufacturing process by absorbing it physically and chemically. Materials that can be used as absorbent are active carbon and basic materials such as NaOH, Ca(OH)2, Mg(OH)2, and the like. In recent years, a chemical resin is widely used an absorbent material.
An important aspect of the absorption type gas scrubber is the identification of the residual lifetime and the replacement time of the absorbent material. After a continuous usage of the absorbent material in the canister, the absorbent material no longer absorbs the harmful gas due to loss of absorbing power. Accordingly, the absorbent material in the canister must be replaced with new material in order to clean the exhaust gas. For purposes of determining the replacement time of the absorbent material, there are generally three methods. The first method is the measurement of a weight change of the canister in a gas scrubber. The second method is the detection of a temperature change caused by absorption heat generated when the absorbent material adsorbs the harmful gas. The third method is using a gas detector of an electrolyte type.
In relation to the the second method, Korean Laid-Open patent Publication No. 2002-0034406 has proposed a method of identifying the residual lifetime and the replacement time of an absorbent material by detecting the absorption heat using temperature sensors installed in the upper, middle, and lower part of a canister. This method is based on the theory that no absorption heat is generated when the absorbing power of the absorbent material in the canister is depleted. Then, there are no temperature changes in the upper, middle, and lower part of the canister. In this method, however, since the residual lifetime of the absorbent material according to the temperature change cannot be confirmed correctly, there is a difficulty in determining the exact time to replace the absorbent material.
For the absorption type gas scrubber used in recent years, an electrolyte type gas detector is widely adapted for identifying the lifetime of the absorbent material in the canister. In this method, the residual lifetime and the replacement time are identified by monitoring the concentration of harmful components in the exit gas by the electrolyte type gas detector. In other words, when the concentration of the harmful component in the exit gas is larger than a predetermined value, the color of the electrolyte in the gas detector is changed by reaction with the exhaust gas. This change of color is transmitted to a control unit by a sensor, and then the control unit releases a warning alarm that the life time of the absorbent material has been exceeded, thereby informing a operator that the absorbent material in the canister has to be replaced.
However, the electrolyte type detector does not inform an operator of the residual lifetime of the absorbent material instantly and continuously. That is, this method informs the operator of the residual lifetime of the absorbent material by transmitting a single warning sound when the replacement time is reached. Therefore, if the operator does not hear a warning sound, confirmation of the loss of absorbing power of the absorbent material does not occur. Accordingly, the gas scrubber is operated without replacing the inactive absorbent material, which can cause environmental problems.
Also, due to the volatility of the electrolyte in the detector, the detector should be replaced periodically even though it has not been used. That is, regardless of the operation of the gas scrubber, the electrolyte in the detector cannot be used after a certain period of time (normally 6 months) because of its volatility. Therefore, the absorbing power of an absorbent material should be maintained by periodically replacing the detector, which is very costly since the replacement process is very complicated.
Owing to these problems, and from a practical standpoint, the detector cannot be replaced in a timely, periodic manner. Thus, the absorbent material in the gas scrubber loses its power, which results in the environmental contamination due to the escape of harmful gas. That is, when the user misses the warning sound of the detector, or if periodical replacement of the detector is not performed, the process will not operate so that the absorbent material has enough absorbing power. Accordingly, a harmful gas will be discharged without cleaning.
To solve the above problems, the present invention provides a gas scrubber including a detector for identifying the residual lifetime of an absorbent material.
The present invention further provides a method of visually identifying the residual lifetime and replacement time of an absorbent material instantly and continuously.
In accordance with an aspect of the present invention, the detector for identifying the residual lifetime of an absorbent material includes, a solid chemical material, the color of which changes when it comes in contact with an untreated exit gas due to loss of absorbing power of the absorbent material, a detection window which contains the solid chemical material, and through which the color change of the solid chemical material can be visually detected from a location outside the gas scrubber with bare eyes. A connecting unit may be placed on the upper and lower part of the detection window.
The detection window of the detector can be formed of a material strengthened to withstand the pressure of a gas passing through the detector, such as a strengthened glass.
The solid chemical material in the detection window can contain a metal component, the color of which changes when the metal contacts the untreated flammable gas and the gas. The solid chemical material can also contain a metal oxide in which manganese is the main component. Also, the solid chemical material contained in the detection window is formed of a plurality of particles that can be visually identified. Preferably, the average diameter of the particles is about 2.0 mm and the average length is about 7 mm. Also, it is preferable that the average specific surface of the solid chemical material is about 170 m2/g, the average specific volume of pores is about 0.9 cc/g, and the average density is about 0.73 g/cc.
In accordance with another aspect of the present invention, a gas scrubber includes an canister for purifying the process gas or cleaning the gas, and a detector for identifying the residual lifetime of the absorbent material contained in the absorbent canister. The detector for detecting the residual lifetime of the absorbent material includes a solid chemical material, the color of which changes when it reacts with untreated exhaust gas discharged due to loss of the absorbing power of the absorbent material, a detection window, which contains the solid chemical material, through which the color change of the solid chemical material can be visually detected from the outside, and connecting units placed on the upper and lower part of the detection window.
The gas scrubber may include pipelines connecting the front end and rear end of the absorbent canister, and the front end and rear end of the detector. Also, the gas scrubber may further include an enclosing cabinet. In this case, the detector is installed in the enclosing cabinet, and a viewing window can be placed on the surface of the enclosing cabinet to detect therethrough the color change of the solid chemical material in the detector from the outside of the cabinet. However, for an easy detection of the color change of the absorbent material by a scrubber operator, the detector can be installed outside of the enclosing cabinet of the gas scrubber.
Also, the above gas scrubber can include a camera for taking pictures of the solid chemical material in the detector. The gas scrubber further includes a display device for connecting the camera. In this case, the pictures are shown on the displaying device to allow the scrubber operator to observe the color change of the solid chemical material. Also, the gas scrubber further comprises a brightness sensor for detecting the brightness of the solid chemical material in the detector. In addition, the gas scrubber further comprises a control unit for determining the residual lifetime and the replacement time of the absorbent material by comparing a brightness value with a predetermined value. The brightness value is obtained by digitalizing of a signal transmitted from the brightness sensor by the control unit. The control unit is connected to the display device to display the brightness value data. When the measured brightness value falls below the predetermined value, the control unit makes the alarm device release a warning alarm.
In accordance with another aspect of the present invention, a method of identifying the residual lifetime of an absorbent material in a gas scrubber comprises the steps of inducing an exhaust gas, which has passed through an absorbent canister in the gas scrubber, to a detector for identifying the residual lifetime of the absorbent material, and detecting the color change of a solid chemical material in the detector through a detection window.
In this case, the color change of the solid chemical material can be visually detected through the detection window. Also, when the detector is enclosed with an enclosing cabinet, the color change of the solid chemical material can be detected by visually observing the solid chemical material through the viewing window placed on the surface of the enclosing cabinet.
As another way of identification of the residual lifetime of the absorbent material, the detection of the color change of the solid chemical material through the detection window can be made by observing pictures of the solid chemical material obtained by a camera disposed in the gas scrubber. In this case, the pictures can be displayed on a display device that is connected to the camera.
Also, as another method of identifying the residual lifetime of the absorbent material, the color change of the solid chemical material through the detection window can be detected by a brightness sensor installed in the gas scrubber and a control unit connected to the brightness sensor. In this case, the control unit digitizes a brightness signal transmitted from the brightness sensor into a brightness value, and then the brightness value is compared with a predetermined value identify the residual life time and the replacement time of the absorbent material. The control unit is connected to the display device to display the brightness value data. Since the control unit is also connected to the warning device, the control unit makes the alarm device release a warning alarm when the measured brightness value falls below the predetermined value.
Hereinafter, the present invention will be described more fully with reference to the accompanying drawings. However, this invention may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, theses embodiments are provided so that this disclosure is thorough and complete and fully conveys the concept of the invention to those skilled in the art.
Referring to
The detection window of the detector 50 depicted in
The solid chemical material in the detector 50 is for monitoring harmful chemicals. The color of the solid chemical material is changed when it comes in contact with untreated harmful exhaust gas. If the harmful components in the process gas or cleaning gas were removed by passing through the absorbent material in the gas scrubber, the purified exhaust gas does not change the color of the solid chemical material in the detector 50. However, if the absorbent material in the gas scrubber exceeded its lifetime and lost the absorbing power, then a significant amount of harmful components could be included in the exhaust gas, thereby resulting in the color change of the solid chemical material. Accordingly, the absorbing power of the absorbent material can be monitored. The solid chemical material can help monitor not only the harmful gas having flammable components such as SiH4, NH3, and AsH3, but also the harmful gas containing acidic components such as NF3 and HF.
The color of the solid chemical material may be slowly changed from the lower end toward upward with the decrease in the absorbing power of the absorbent material. If the absorbent material loses substantially completely its absorbing power due to exceeding its lifetime, the color of the solid chemical material turns into a strong color shade. As the absorbing power of the absorbent material decreases, the color change of the solid chemical material diffuses gradually from the lower end toward upward and the degree of color becomes stronger. According to an embodiment of the present invention, the color of the solid chemical material turns into a low brightness color such as grey when it reacts with the harmful gas, and the brightness of the color is further lowered as the absorbent material loses its absorbing power. Therefore, the detector according to an embodiment of the present invention enables a continuous detection of the residual lifetime of the absorbent material.
The solid chemical material in the detector 50 contains metal components, the color of which changes when the absorbent material comes in contact with a flammable and acidic gas. Preferably, a metal oxide containing manganese as the main component is used in the solid chemical material. Preferably, the solid chemical material is formed of small solid particles having an average diameter of about 2.0 mm and an average length of about 7 mm. Also, preferably, the average specific surface of the particles is about 170 m2/g, and the average density is about 0.73 g/cc. Particles have small pores on their surface, and preferably, the specific volume of the pores is about 0.9 cc/g.
When the color of the solid chemical material changes substantially completely, the absorbent material must be replaced. In this case, the solid chemical material should also be replaced for continuous monitoring of the new absorbent material. The replacement of the solid chemical material with a new one can be simply conducted by dismantling the connecting units 56 and 58. The cost of the solid chemical material used for the detector according to an embodiment of the present invention is significantly lower than the cell cost of the conventional electrolyte type detector.
Moreover, in the conventional electrolyte type detector, the electrolyte in a cell has to be replaced at least twice a year due to the volatility of the electrolyte, even if a scrubber has not been operated. However, the solid chemical material in the detector according to an embodiment of the present invention does not need to be replaced if it has not been operated. The solid chemical material needs to be replaced when the color of the solid chemical material has changed completely after lifetime of the absorbent material exceeds. Accordingly, the use of a detector according to an embodiment of the present invention reduces installation costs during replacement of the chemicals compared to the conventional electrolyte type detector.
Hereinafter, referring to the
Referring to
The exhaust gas passed through the canister 20 enters into a detector 50 for detecting the residual lifetime of the absorbent material. A solid chemical material for detecting the residual lifetime of the absorbent material is filled in the detector 50. Since the solid chemical material is stored in a detector having a transparent detection window, a color change of the solid chemical material can be detected through the detection window. The exhaust gas passed through the detector 200 is discharged to outside through an outlet. In this case, if the absorbing power of the absorbent material in the canister 20 is at a normal level, the harmful components in the exhaust gas can be removed by the absorbent material. Accordingly, the exhaust gas does not change the color of the solid chemical material in the detector 200. However, if the absorbing power of the absorbent material is lost to a certain degree, a significant amount of the harmful components remained in the exhaust gas even after the exhaust gas passed through the canister 20. Accordingly, the color of the solid chemical material changes from the lower end toward upward in the detection window. If the absorbing power of the absorbent material is completely lost, the color of the solid chemical material changes into a strong color. According to an embodiment of the present invention, the color of the solid chemical material may be changed to a darker color as the result of the reaction with the harmful component in the gas.
Also, in the present invention, the gas scrubber 200 comprises an enclosing cabinet 24 having a canister 20 and a detector 50 for identifying the residual lifetime of the absorbent material therein. A viewing window 23 is placed on the surface of the enclosing cabinet 24 to observe the solid chemical material in the detector 50 from outside. The color change of the solid chemical material in the detector 50 can be detected through this viewing window 23. However, the gas scrubber can be used without the enclosing cabinet 24.
The gas scrubber 300 depicted in
The gas scrubber 400 depicted in
Since the camera 42 is connected to a display device 45, the pictures taken by the camera 42 are displayed on the display device 45 in real time. Accordingly, the installation of a viewing window on the surface of the enclosing cabinet 44 for visually identifying the color change is not necessary. By observing the pictures of the solid chemical material on the display device 45, identification of the residual lifetime of the absorbent material can be made. Moreover, the display device 45 can be placed on a remote location from the system, such as a gas scrubber operator can conveniently identify the residual lifetime of the absorbent material from a distance location.
Referring to
As depicted in
When the absorbing power of the absorbent material is at a normal level, the exhaust gas passed through the absorbent material does not change the color of the solid chemical material in the detector 50. However, if the absorbing power of the absorbent material is lost, the exhaust gas passed through the absorbent material changes the color of the solid chemical material in the detector 50 into a darker color.
The color change of the solid chemical material according to the absorbing power of the absorbent material is detected by the brightness sensor 62 installed in front of the detector 50. The brightness signal obtained by the brightness sensor 62 is transmitted to the control unit 66 that is connected to the brightness sensor 62. The control unit 66 comprises an A/D (alternative/direct) converter 66a. The A/D converter digitizes the brightness signal received from the brightness sensor 62 into a brightness value. The digitized brightness value is then inputted to a microprocessor 66b and is compared to a predetermined value. The predetermined value is a predetermined brightness value for determining the replacement time of the absorbent material. If the measured brightness value is lower than the predetermined value, the absorbing power of the absorbent material is lost. Accordingly, the absorbent material should be replaced.
The control unit 66 is connected to the display device 69 so that the brightness value data is displayed on the display device 69. The brightness value data displayed on the display device is displayed in a digital form or in a form of a bar graph or the like. The display device 69 can display not only the measured brightness value, but also differences between the measured brightness value and the predetermined value. Also, an alarm device 68 is connected to the control unit 66. If the measured brightness value falls below the predetermined value, the control unit 66 sends a signal to the alarm device 68 for transmitting a warning alarm.
When using a gas scrubber according to an embodiment of the present invention, a color change of the solid chemical material is detected through a detection window, which enables continuous confirmation of a residual lifetime and replacement time of an absorbent material, thereby making the management of the gas scrubber easy.
Referring to
The process gas enters into a process gas scrubber 200a after passing through the vacuum pump 209 via a coupling valve 211. The coupling valve 211 opens a designated one of two pipelines connected thereto. Accordingly, by manipulating the coupling valve 211, either automatically or manually, the flow of exhaust gas can be controlled such that the process gas flows only into the process gas scrubber 200a, and the cleaning gas flows only into a cleaning gas scrubber 200b.
The process gas flowing into the process gas scrubber 200a is purified by the process gas scrubber 200a, and is discharged into the atmosphere after a final treatment in a large process gas scrubber 210a. The large process gas scrubber 210a mainly combusts the gas.
When the process is completed, a cleaning gas is supplied to the process facility 207 for cleaning the process chamber of the process facility 207. The cleaning gas enters into the cleaning gas scrubber 200b via the coupling valve 211 after passing through the vacuum pump 209. The cleaning gas enters and is purified in the cleaning gas scrubber 200b. The gas is discharged into the air after final treatment in a large cleaning gas scrubber 210b. The large cleaning gas scrubber 210b mainly combusts the gas.
The exhaust gas passing through the process gas scrubber 200a or the cleaning gas scrubber 200b is purified by passing through a canister installed in the gas scrubber 200a or 200b. In order to identify whether the absorbing power of the absorbent material is at a normal level, a detector 50a or 50b according to an embodiment of the present invention is placed in the exit gas stream of the gas scrubber 200a and 200b. A viewing window 23a or 23b is installed on an enclosing cabinet of the gas scrubber 200a or 200b so as to observe the detector 50a or 50b through the viewing window 23a or 23b. A gas scrubber operator can identify the residual lifetime of absorbent material continuously by observing the color change of a solid chemical material within the detection window, through the detection window of the detector 50a or 50.
According to an embodiment of the present invention, by visually observing the color change of a solid chemical material through a detection window, the residual lifetime and replacement time of an absorbent material can be identified instantly and continuously. Thus, the absorbent material in a gas scrubber can be managed correctly and easily, which enhances the reliability of the gas scrubber.
Also, according to an embodiment of the present invention, the color change of the solid chemical material can be monitored by a display device from a remote place by observing the pictures taken by a camera installed in front of a detection window. In addition, the color change of the solid chemical material can be monitored by a display device from a remote place by observing the brightness data taken by a brightness sensor installed in front of a detection window. Accordingly, a gas scrubber operator can identify the residual lifetime and the replacement time of an absorbent material more conveniently and safely.
Also, since a detector according to an embodiment of the present invention clearly notifies the correct time to replace an absorbent material or canister, the detector significantly reduces the danger of discharging untreated harmful gas into the atmosphere. In other words, the environmental protection from the process gas and cleaning gas can be effectively achieved by using a detector according to an embodiment of the present invention.
Also, the cost of a solid chemical material in a detector according to an embodiment of the present invention is remarkably lower than that of an electrolyte cell for the conventional electrolyte type detector. For a detector according to an embodiment of the present invention, the solid chemical material does not need to be replaced if the gas scrubber has not been operated. The solid chemical material has to be replaced only when the color of the solid chemical material has substantially completely changed due to the loss of lifetime of the absorbent material. Therefore, the maintenance cost of the gas scrubber can be minimized by reducing the installation cost of a detector and the replacement cost of an absorbent material in the detector.
Although the preferred embodiments of the present invention have been described in detail hereinabove, it should be understood that many variations and/or modifications of the basic inventive concepts herein taught, which may appear to those skilled in the art, will still fall within the spirit and scope of the present invention as defined in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-58250 | Aug 2003 | KR | national |
