JP4449686B2 - Chemical air filter operation control system - Google Patents

Description

  The present invention relates to a chemical air filter operation control system, and more particularly, to a system for controlling a passing air amount of a chemical air filter.

Due to miniaturization and multi-layering associated with high integration of semiconductor devices, various impurities have various effects on semiconductor processes. In semiconductor devices, it is a well-known fact that all elements and molecules other than silicon elements have some influence on the semiconductor process at a very small level of about picogram (10 ⁻¹² g). Examples of molecular contaminants include metals, acid gases, alkaline gases, boron and phosphorus dopants, and organic substances, and those that are likely to adhere to the surface of a semiconductor device are considered to affect the device. For example, there are about 50 kinds of organic substances in a clean room, and the organic substances adhering therein are known to be limited organic substances having a particularly high boiling point and a large molecular weight.

  As a means for removing this molecular pollutant, a chemical air filter is mainly used. This chemical air filter mainly uses activated carbon, and is an effective removal means for almost all molecular contaminants in the atmosphere. Therefore, in order to form a clean space such as a clean room, a chemical air filter is provided on the side where air is supplied to the clean space to remove molecular contaminants from the air supplied to the clean space.

By the way, in order to detect the end point of the chemical air filter, the device installs a sensor with an adsorption film of a required gas component on the electrode of the crystal resonator in the chamber and connects a frequency detector to the sensor. A method of detecting the end point of a chemical air filter by taking out the amount of contaminants attached to the sensor with a frequency detector as a resonance frequency change and quantifying the components in the gas based on this resonance frequency change. (See Patent Document 1).
JP 2002-168748 A

  However, if the chemical air filter is operated at all times, for example, for organic substances, most of the adsorption sites of the chemical air filter will be occupied by low and medium boiling organic substances that are difficult to adhere to the product surface. There was a problem of short.

In addition, when molecular contaminants that are likely to adhere to the product surface suddenly occur in the clean space, there is no way to monitor the amount of contamination on the product surface in real time, so the air flow rate of the chemical air filter remains constant. In some cases, it takes time to completely remove the generated molecular contaminants.
Therefore, it is necessary to extend the life of the chemical air filter and to quickly remove it when molecular contaminants are generated.

  It is an object of the present invention to provide a chemical air filter operation control system that extends the life of a filter that removes contaminants by monitoring the contaminants attached to the product surface in the clean space.

In order to achieve the above object, a chemical air filter operation control system according to the present invention includes a chemical air filter that removes contaminants from the air circulating through a clean space, and an air volume adjustment that causes the chemical air filter to ventilate the air. Provided in the input stage of the clean space, a surface acoustic wave sensor for detecting the contaminant generated in the clean space is provided in the clean space, and the difference between the output value changes of the surface acoustic wave sensor is preset. A chemical air filter operation control system provided with means for comparing with a reference value and controlling the air volume adjusting means according to the comparison value, wherein the surface acoustic wave sensor forms an electrode on a piezoelectric substrate and the result in the adsorption film of contaminants formed on at least the upper electrode, the dust removal filter disposed downstream of the chemical filter, before Adsorption film, it becomes the same material as the product surface of the cleaning space, control means for adjusting the air volume obtains the amount of change in the oscillation frequency is changed by the contaminants adsorbed, stored in advance with the amount of change Compared with the reference value, if the amount of change is greater than or equal to the reference value, the air volume by the air volume adjusting means can be increased, and if the amount of change is less than the reference value, a signal for decreasing the air volume by the air volume adjusting means can be output. The air supply amount supplied into the clean space can be output so as to be set to the minimum air flow rate that satisfies the cleanliness required for the clean space at normal times .
The clean space may be a mini environment, a stocker, a clean booth, or a clean room.

Further, the air in the clean space is discharged from the clean space, the discharge port and the air volume adjusting means are connected by a return duct, and the air is circulated through the clean space. The motor branch is provided between the motor damper and the other path is provided with the motor damper and the chemical filter at the subsequent stage .

  When the detection sensor detects a contaminant, the output value of the detection sensor changes. When the difference between the changes and the reference value are compared and the air volume adjusting means is controlled in accordance with the comparison value, the passing air volume of the chemical air filter changes. If the amount of air passing through the chemical air filter is increased when the amount of pollutant increases in the clean space and the difference in output value change exceeds the reference value, the pollutant is quickly discharged from the clean space by the air and discharged. The contaminated contaminants can be removed with a chemical air filter. Therefore, when contaminants increase in the clean space due to some factor, the contaminants can be quickly removed from the clean space. In addition, if the contaminants decrease and the difference becomes less than the reference value, controlling the flow rate of the chemical air filter to reduce the flow of the chemical air filter can minimize the load on the chemical air filter. Life can be extended.

  In addition, when the contaminant is adsorbed on the quartz resonator sensor or the surface acoustic wave sensor, the oscillation frequency, which is the output value from the sensor, changes, so whether or not the contaminant in the clean space has increased by measuring this oscillation frequency. Can be determined. In addition, since the oscillation frequency of the quartz vibrator sensor and surface acoustic wave sensor changes depending on the mass of the substance adsorbed on the sensor, the amount of contaminant in the clean space increases by measuring the mass of the contaminant adsorbed on the sensor surface. It can also be determined whether or not.

  Further, since the same substance as the product surface in the clean space is coated on the quartz vibrator sensor or the surface acoustic wave sensor, the contaminants adhering to the product surface are also adsorbed on the adsorption film. Therefore, it is possible to monitor the contaminants that are adsorbed on the product surface, so that the amount of air passing through the chemical air filter can be increased when the contaminant adsorbed on the product surface increases in the clean space. It is possible to extend the service life.

  It can also monitor contaminants in mini-environments, stockers, clean booths or clean rooms, and can be quickly removed when contaminants increase.

  Below, the best embodiment of the chemical air filter operation control system concerning the present invention is described. This embodiment is a chemical air filter operation control system for removing molecular pollutants from air supplied to clean spaces such as clean rooms, mini-environments, stockers, and clean booths. This is a system for controlling the air flow rate through the filter.

  First, the first embodiment will be described. The chemical air filter operation control system uses a quartz resonator sensor or a surface acoustic wave (hereinafter referred to as SAW) sensor as a molecular contaminant detection sensor. FIG. 1 is a schematic cross-sectional view of a crystal resonator sensor. In the quartz oscillator sensor 10 a, excitation electrodes 14 are provided on both surfaces of the center portion of the quartz substrate 12, and an adsorption film 16 that adsorbs molecular contaminants is provided on the excitation electrodes 14. The excitation electrode 14 is made of, for example, a metal such as gold, and is electrically connected to a connection electrode (not shown) formed on the end of the crystal substrate 12 or the like. The adsorption film 16 is formed of the same material as that of the product surface in the clean space. For example, when a semiconductor device using silicon is manufactured in the clean space, the adsorption film 16 is a silicon film. Although the adsorption film 16 is formed only on one excitation electrode 14 in FIG. 1, it may be formed on both excitation electrodes 14.

  FIG. 2 is an explanatory diagram of a surface acoustic wave sensor. 2A is a schematic plan view, and FIG. 2B is a schematic cross-sectional view. In the SAW sensor 10b, a comb-like electrode (interdigital transducer: hereinafter referred to as IDT) 22 is provided on one surface of a quartz substrate 20, and reflectors 26 are provided at both ends of the IDT 22 in the SAW propagation direction. The IDT 22 includes a plurality of electrode fingers 24, and includes an electrode having a configuration in which one end of the electrode finger 24 is short-circuited, and the electrode fingers 24 are alternately engaged with the electrodes facing each other. Such an IDT 22 is electrically connected to a connection electrode (not shown) formed on the quartz substrate 20. The reflector 26 includes a plurality of electrode fingers 28 formed in parallel with the electrode fingers 24 of the IDT 22. An adsorption film 29 is provided on the quartz substrate 20 on which the IDT 22 and the reflector 26 are provided. The adsorption film 29 is formed of the same material as the product surface in the clean space. For example, when a semiconductor device is manufactured using a silicon wafer in the clean space, the adsorption film 29 becomes a silicon film. .

  Note that when the quartz resonator sensor 10a and the SAW sensor 10b are compared, the SAW sensor 10b can oscillate at a higher frequency than the quartz resonator sensor 10a. In the chemical air filter operation control system, since the resolution increases when the oscillation frequency of the detection sensor is increased, the SAW sensor 10b is preferably used when high detection sensitivity is required.

  FIG. 3 is a block diagram illustrating the chemical air filter operation control system. The chemical air filter operation control system 30 has the following configuration. That is, the crystal oscillator sensor 10a or the SAW sensor 10b is connected to an oscillation circuit 32 for causing them to oscillate. Specifically, the oscillation circuit 32 is electrically connected to the connection electrode of the detection sensor 10 (10a, 10b). The oscillation circuit 32 is connected to frequency measuring means 34 that measures the oscillation frequency of the detection sensor 10. The frequency measuring means 34 is connected to an arithmetic control means 36 (36a, 36b) described later, and is provided in the controller 38 together with the oscillation circuit 32 and the frequency measuring means 34.

  Here, in the detection sensor 10, when the substance is adsorbed on the adsorption films 16 and 29, the oscillation frequency changes depending on the mass of the adsorbed substance. That is, the oscillation frequency of the detection sensor 10 decreases from the reference frequency when the substance is adsorbed on the adsorption films 16 and 29 when the stage where the substance is not adsorbed on the adsorption films 16 and 29 is set as the reference frequency. Change.

  FIG. 4 is an explanatory diagram in which the chemical air filter operation control system 30 is applied to a clean space facility. The clean space facility 40 includes a clean space 42 for processing and manufacturing semiconductors, storing products and jigs, and an upper space 44 that is located above the clean space 42 and supplies air to the clean space 42. Prepare. In addition, as a circulation path of the air, a return space 46 that receives the air discharged from the clean space 42 and returns it to the upper space 44 is provided. That is, the clean space 42 is configured to take in clean air from the top and discharge the air together with dust in the clean space 42 from the lower side surface of the clean space 42.

  Between the clean space 42, that is, between the clean space 42 and the top space 44, a chemical air filter (CAF) 48 that removes molecular contaminants from the air and a high performance (HEPA) filter that removes dust or Ultra-high performance (ULPA) filters are provided. In the following, the HEPA filter or ULPA filter is abbreviated as HEPA filter 50. A fan 52 that supplies air to the clean space 42 is provided above the CAF 48 and the HEPA filter 50. The fan 52 serves as an air volume adjusting means for allowing air to flow through the CAF 48. In FIG. 4, the filters 48 and 50 and the fan 52 are described in a form in which one is provided above the clean space 42. However, the present invention is not limited to this form, and the inside of the clean space 42 is cleaned. What is necessary is just to set an installation position and a number suitably so that it may be kept.

The clean space 42 is provided with a molecular contaminant detection sensor 10. One detection sensor 10 may be provided in the clean space 42, or two or more detection sensors 10 may be provided. When a plurality of detection sensors 10 are provided, the adsorption films 16 and 29 of each detection sensor 10 may be formed of different types of materials. The controller 38 is provided outside the clean space facility 40 and is connected to the detection sensor 10 and the fan 52. Then, the arithmetic control means 36a provided in the controller 38 obtains a difference when the oscillation frequency of the detection sensor 10 changes, that is, a change amount (detection value) of the oscillation frequency, and this detection value and a prestored reference value and Are compared. This reference value is set in accordance with the cleanliness required for the clean space 42. The arithmetic control unit 36a controls the rotation speed of the fan 52 according to the amount of change in oscillation frequency when the detection sensor 10 detects the molecular contaminant, that is, the comparison result (comparison value) between the detection value and the reference value. The amount of air supplied to the clean space 42 can be adjusted.
A means 54 for exhausting part of the air in the clean space 42 to the outside of the clean space facility 40 is provided below the clean space 42.

  The upper side of the clean space 42, that is, the upper side of the filters 48 and 50 and the fan 52 is an upper space 44, and air including dust and the like is supplied from the clean space 42 to the upper space 44 through the lettan space 46. Is done. The upper space 44 is provided with means 56 for sucking air from which dust or the like has been removed from outside the clean space facility 40.

  Next, the operation of the chemical air filter operation control system 30 will be described. In the clean space 42, air passes through the CAF 48 and the HEPA filter 50 as the fan 52 rotates, and is supplied with air from which molecular contaminants and dust are removed. The supplied air contains molecular contaminants and dust when passing through the clean space 42 and is discharged from the clean space 42. Then, the discharged air is supplied to the upper space 44 via the lettan space 46. Thereby, air circulates through the clean space facility 40. Note that the air supply amount to the clean space 42 is normally set to an amount (minimum air volume) that satisfies the cleanliness required for the clean space 42.

  At this time, the detection sensor 10 is oscillated by the oscillation circuit 32 and the oscillation frequency of the detection sensor 10 is measured by the frequency measuring means 34 in order to detect the molecular contaminant adsorbed in the clean space 42, that is, the product. The arithmetic control unit 36 a inputs the oscillation frequency of the detection sensor 10 obtained by the frequency measuring unit 34.

  When the molecular contaminant is adsorbed on the detection sensor 10, the oscillation frequency of the detection sensor 10 changes, and the difference between these oscillation frequencies, that is, the change amount (detection value) of the oscillation frequency is obtained by the arithmetic control means 36a. The arithmetic control unit 36a compares the detected value with a reference value stored in advance, and outputs a signal for increasing the rotational speed to the fan 52 if the detected value is equal to or greater than the reference value. When this signal is input, the fan 52 increases the rotational speed. As a result, the amount of air passing through the CAF 48 and the HEPA filter 50 increases, and the amount of air supplied to the clean space 42 increases. Accordingly, since the molecular contaminants in the clean space 42 are discharged in a short time as the amount of air increases, the molecular contaminants in the clean space 42 can be removed in a short time.

  As the molecular contaminants in the clean space 42 decrease, the amount of change in the oscillation frequency of the detection sensor 10 decreases. At this time, the arithmetic control unit 36a compares the detection value of the detection sensor 10 with the reference value, and outputs a signal for reducing the rotational speed to the fan 52 if the detection value is less than the reference value. The fan 52 decreases the rotational speed when this signal is input. As a result, the amount of air passing through the CAF 48 and the HEPA filter 50 decreases, the amount of air supplied to the clean space 42 decreases, and it becomes possible to return to the normal air supply amount.

  As described above, the detection sensor 10 is provided with electrodes on the quartz substrates 12 and 20, and at least the adsorption films 16 and 29 made of the same material as the product surface in the clean space 42 are provided on the electrodes. It can always measure molecular contaminants adhering to the surface. In this detection sensor 10, when the molecular contaminant is adsorbed on the adsorption films 16 and 29, the oscillation frequency changes. Therefore, by detecting the oscillation frequency change of the detection sensor 10, the molecular contaminant is detected in the clean space 42. You can see that it exists. Then, by comparing the amount of change (detection value) in the oscillation frequency of the detection sensor 10 with the reference value, whether or not the clean space 42 has the required cleanliness, that is, the product surface in the clean space 42 is detected. It can be judged whether there are many or few molecular contaminants adhering.

  When the detected value is compared with the reference value, if the detected value is equal to or higher than the reference value, it can be determined that the cleanliness required for the clean space 42 has not been reached, so the fan 52 is controlled to control the CAF 48 or HEPA. The amount of air passing through the filter or the like 50 is increased, that is, the amount of air supplied to the clean space 42 is increased to discharge molecular contaminants from the clean space 42, and molecular contaminants in the clean space 42 are removed. It can be removed in a short time.

  When the molecular contaminants in the clean space 42 are removed and the clean space 42 reaches the required cleanliness, the amount of change in the oscillation frequency of the detection sensor 10 becomes small, and the detected value becomes less than the reference value. In this state, the fan 52 is controlled to reduce the amount of air passing through the CAF 48, HEPA filter, etc. 50, and the air supplied to the clean space 42 can be returned to the minimum amount. Therefore, the amount of air supplied to the CAF 48, the HEPA filter, etc. 50 does not always need to be increased in order to remove molecular contaminants in the clean space 42, and molecular contaminants are not present in the clean space 42. Since it increases when it increases, the load on the CAF 48 can be minimized, and the life of the CAF 48 can be extended.

  In the above-described embodiment, the quartz vibrator sensor 10a and the SAW sensor 10b have been described using a quartz substrate, but a piezoelectric substrate made of another piezoelectric material can also be used. In this case, a vibrator sensor or an SAW sensor can be formed by forming an excitation electrode or IDT on a piezoelectric substrate formed of a piezoelectric material such as lithium tantalate, lithium niobate, or zinc oxide.

The detection sensor 10 has an oscillation frequency that varies depending on the mass of the molecular contaminant adsorbed on the detection sensor 10. Therefore, the oscillation frequency output from the detection sensor 10 may be converted into mass, the difference in mass change may be compared with a reference value, and the rotational speed of the fan 52 may be controlled according to the comparison value.
In addition, the detection sensor can be configured without an adsorption film.

  Next, a second embodiment will be described. In the second embodiment, the same reference numerals are given to the same components as those in the first embodiment, and the description thereof is omitted or simplified. FIG. 5 is an explanatory diagram in which the chemical air filter operation control system is applied to a clean space facility. The clean space facility 60 includes a clean space 62, and a HEPA filter or ULPA filter is provided above the clean space 62. In the following, the HEPA filter or ULPA filter is abbreviated as HEPA filter 50. On the upper side of the HEPA filter etc. 50, a fan 63 for supplying a constant air volume of air to the HEPA filter etc. 50 is provided. The clean space 62 is provided with means 56 for sucking air from which dust or the like has been removed from the outside of the clean space facility 60, and a part of the air in the clean space 62 is directed to the outside of the clean space facility 60 at the bottom. Means 54 are provided for evacuating.

  In this configuration, air is discharged together with dust in the clean space 62 from the lower side surface of the clean space 62, and the exhaust port and the fan 63 are connected to each other by the return duct 64 so that the air circulates through the clean space 62. is there. The letter duct 64 is divided into two paths in between. The motor damper 66 is provided in one path 64a, the motor damper 68 is provided in the other path 64b, and the CAF 48 is provided in the subsequent stage. The motor damper 68 provided in the other path 64b serves as an air volume adjusting means for ventilating the CAF 48 with air.

  In the clean space 62, the detection sensor 10 is provided. The detection sensor 10 may be the crystal resonator sensor or SAW sensor described in the first embodiment. The detection sensor 10 is connected to a controller 38 provided with an oscillation circuit 32, a frequency measurement unit 34, and an arithmetic control unit 36b. The arithmetic control unit 36b obtains a difference when the oscillation frequency of the detection sensor 10 changes, that is, a change amount (detected value) of the oscillation frequency, and compares the detected value with a prestored reference value. . The arithmetic control unit 36b is connected to motor dampers 66 and 68 provided in each of the two paths of the reductant duct 64, and the amount of change in oscillation frequency when the molecular contaminant is detected by the detection sensor 10, that is, the detected value and the reference The opening degree of each motor damper 66, 68 is adjusted according to the comparison result (comparison value) with the value.

  Next, the operation of the chemical air filter operation control system will be described. In the clean space 62, air passes through the HEPA filter 50 and the like by rotation of the fan 63, and air from which dust is removed is supplied. The supplied air contains dust when passing through the clean space 62 and is discharged from the clean space 62. The discharged air is supplied to the fan 63 via one path 64a in the reductant duct 64. At this time, the opening degree of the motor damper 66 provided in one path 64a is 100%, and the motor damper 68 provided in the other path 64b is closed. In such a clean space facility 60, the retan air in the clean space 62 is circulated by the fan 63 via the retan duct 64.

  At this time, the detection sensor 10 is oscillated by the oscillation circuit 32 and the oscillation frequency of the detection sensor 10 is measured by the frequency measuring means 34 in order to detect molecular contaminants adsorbed on the product in the clean space 62. The arithmetic control unit 36 b inputs the oscillation frequency of the detection sensor 10 obtained by the frequency measuring unit 34.

  When the molecular contaminant is adsorbed on the detection sensor 10, the oscillation frequency of the detection sensor 10 changes, and the difference between the oscillation frequencies, that is, the change amount (detection value) of the oscillation frequency is obtained by the arithmetic control means 36b. The arithmetic control unit 36b compares the detected value with a reference value stored in advance, and if the detected value is equal to or greater than the reference value, a signal for narrowing the opening degree with respect to the motor damper 66 provided in one path 64a. While outputting, the signal which raises an opening degree is output with respect to the motor damper 68 provided in the other path | route 64b. When each motor damper 66, 68 receives a signal, it adjusts the opening according to the signal. As a result, air is supplied to the CAF 48, and molecular contaminants are removed by the CAF 48. Further, when the opening degree of the motor damper 68 at the front stage of the CAF 48 is adjusted according to the change amount of the oscillation frequency of the detection sensor 10, that is, the opening degree of the motor damper 68 at the front stage of the CAF 48 is increased as the change amount of the oscillation frequency is larger. Molecular contaminants in 62 can be quickly removed. In addition, if the opening degree of each motor damper 66 and 68 is totaled and it controls so that it may always become 100%, it will become possible to make the passing air volume of 50, such as a HEPA filter, constant.

  As the molecular contaminants in the clean space 62 decrease, the amount of change in the oscillation frequency of the detection sensor 10 decreases. At this time, the arithmetic control unit 36b compares the detection value in the detection sensor 10 with the reference value, and outputs a closing signal to the motor damper 68 provided in the preceding stage of the CAF 48 if the detection value is less than the reference value. At the same time, a signal for setting the opening degree to 100% is output to the motor damper 66 provided in the one path 64a. When each motor damper 66, 68 receives a signal, it adjusts the opening according to the signal. As a result, air is not supplied to the CAF 48, and the air circulates through the one path 64a.

  Thus, when the amount of change in the oscillation frequency of the detection sensor 10 is compared with the reference value, it can be determined that the cleanliness required for the clean space 62 has not been reached if the amount of change is equal to or greater than the reference value. While reducing the opening degree of the motor damper 66 provided in the one path 64a and increasing the opening degree of the motor damper 68 in front of the CAF 48 to supply air to the CAF 48, molecular contaminants in the clean space 62 are removed. It can be removed in a short time.

  When the molecular contaminants in the clean space 62 are removed and the clean space 62 reaches the required cleanliness, the amount of change in the oscillation frequency of the detection sensor 10 becomes small, and the detected value becomes less than the reference value. In this state, the motor damper 68 in the front stage of the CAF 48 is closed and the opening of the motor damper 66 in the one path 64a is set to 100%, so that the load on the CAF 48 can be minimized and the CAF 48 has a long service life. Can be achieved.

  Furthermore, the clean space 62 can always be supplied with a constant amount of air. Therefore, when the amount of air supplied to the clean space changes, dust and the like may rise depending on the cleanliness required for the clean space when the air supply amount increases. There is no fear of flying.

The detection sensor 10 has an oscillation frequency that varies depending on the mass of the molecular contaminant adsorbed on the detection sensor 10. Therefore, the oscillation frequency output from the detection sensor 10 may be converted into mass, the difference in mass change may be compared with a reference value, and the opening degree of the motor damper 68 may be controlled according to the comparison value.
In addition, the detection sensor can be configured without an adsorption film.

It is a schematic sectional drawing of a crystal oscillator sensor. It is explanatory drawing of a surface acoustic wave sensor. It is a block diagram explaining a chemical air filter operation control system. It is explanatory drawing which applied the chemical air filter operation control system to the clean space installation concerning 1st Embodiment. It is explanatory drawing which applied to 2nd Embodiment and applied the chemical air filter operation control system to the clean space installation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Detection sensor, 30 ... Chemical air filter operation control system, 32 ... Oscillator circuit, 34 ... Frequency measuring means, 36 (36a, 36b) ... Calculation control means, 42 ... Clean space, 48 ......... Chemical air filter (CAF), 50 ......... HEPA filter, etc. 52 ......... Fan, 62 ...... Clean space, 63 ......... Fan, 66, 68 ...... Motor damper.

Claims (3)

The pollutant generated in the clean space is provided with a chemical air filter for removing pollutants from the air circulating through the clean space and an air volume adjusting means for venting air through the chemical air filter at the input stage of the clean space. A surface acoustic wave sensor for detecting the surface acoustic wave is provided in the clean space, the difference in output value change of the surface acoustic wave sensor is compared with a preset reference value, and the air volume adjusting means is controlled according to the comparison value. A chemical air filter operation control system provided with means,
The surface acoustic wave sensor is formed with an electrode on a piezoelectric substrate, and an adsorption film of the contaminant is formed on at least the electrode,
A dust removing filter is arranged at the subsequent stage of the chemical filter,
The adsorption film is made of the same material as the product surface in the clean space,
The control means for adjusting the air volume obtains the amount of change of the oscillation frequency that changes due to the adsorption of the pollutant, and compares this amount of change with a pre-stored reference value. The air volume by the air volume adjusting means is increased, and if the amount of change is less than a reference value, a signal for decreasing the air volume by the air volume adjusting means can be output. It is possible to output so that the minimum air volume that satisfies the cleanliness required for the clean space is set.
A chemical air filter operation control system characterized by the above.   3. The chemical air filter operation control system according to claim 1, wherein the clean space is a mini environment, a stocker, a clean booth, or a clean room.   The air in the clean space is discharged from the clean space, the discharge port and the air volume adjusting means are connected by a return duct, and the air is circulated through the clean space. The motor branch is provided in one of the paths, and the motor damper is provided in the other path and the chemical filter is provided in the subsequent stage thereof. The chemical air filter operation control system described.

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