CA2290922C - Flow control apparatus for a semiconductor manufacturing wet bench - Google Patents
Flow control apparatus for a semiconductor manufacturing wet bench Download PDFInfo
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- CA2290922C CA2290922C CA002290922A CA2290922A CA2290922C CA 2290922 C CA2290922 C CA 2290922C CA 002290922 A CA002290922 A CA 002290922A CA 2290922 A CA2290922 A CA 2290922A CA 2290922 C CA2290922 C CA 2290922C
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- flow
- operational mode
- duct
- rate
- air
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
- H01L21/67005—Apparatus not specifically provided for elsewhere
- H01L21/67011—Apparatus for manufacture or treatment
- H01L21/67017—Apparatus for fluid treatment
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
- H01L21/67005—Apparatus not specifically provided for elsewhere
- H01L21/67011—Apparatus for manufacture or treatment
- H01L21/67017—Apparatus for fluid treatment
- H01L21/67063—Apparatus for fluid treatment for etching
- H01L21/67075—Apparatus for fluid treatment for etching for wet etching
Abstract
Apparatus for controlling the volume of air that is supplied and exhausted from a electronic semiconductor manufacturing wet bench is disclosed.
The volume of air that is exhausted from the wet bench is increased during predetermined portions of the manufacturing process and is reduced during noncritical times as a function of predetermined conditions that may be detected or otherwise determined during the manufacturing process.
The volume of air that is exhausted from the wet bench is increased during predetermined portions of the manufacturing process and is reduced during noncritical times as a function of predetermined conditions that may be detected or otherwise determined during the manufacturing process.
Description
3 The present invention relates generally to the control of the ventilation 4 of a wet bench for manufacturing electronic semiconductor products and more particularly to a apparatus for controlling the exhausting of fumes that are produced 6 during the manufacturing of such electronic semiconductor products in a way which 7 conserves energy costs without sacrificing safety.
8 Manufacturing stations for manufacturing many types of electronic 9 semiconductor products are known in the electronic industry as wet benches.
A wet bench is a process equipment tool that is used to etch semiconductor wafers during 11 the manufacturing of them. The etching is done by acids that are inherently 12 dangerous to individuals that may be present in the area, and for that reason, the acid 13 fumes must be expelled during and after use of the acid during the manufacturing 14 process. The wet benches generally have an enclosure which has an access door for users, and the enclosure is typically connected to an exhaust system for removing the 16 noxious fumes so that the users will not be exposed to them.
17 Wet benches are typically used intermittently throughout a work day.
18 Each time they are used, a tank associated with the wet bench is filled with acid, 19 which is then expelled after the semiconductotr wafers are etched. During the filling and use of the acid, the fumes produced must be exhausted to prevent any contact 21 with users. Manufacturers of semiconductors are generally not concerned with the 22 amount of flow of air that is moved through the interior of the wet bench enclosures, 1 and the flow is generally constant regardless of the presence or impounding presence 2 of acid being introduced or when the wet bench is idle.
3 The volume of air that is moved through a wet bench can significantly 4 impact on the cost of operating the wet bench. Since the replacement air that is S introduced into the wet bench must be clean room quality air, it has to be processed 6 and filtered to remove any particles that could otherwise contaminate the 7 semiconductor wafers during their manufacture. It is also necessary to condition the 8 air with respect to its temperature and humidity and there are also costs associated 9 with such conditioning. Also, exhausted air from the wet bench must have acid fumes removed from the exhaust before the air can be vented to atmosphere.
11 With respect to the costs associated with operation of a wet bench, clean 12 room replacement air can cost as high as $50-$60 per cubic foot per minute per year 13 as well as additional scrubbing for EOC incineration costs which can range from $30-14 $150 per cubic foot per minute (CFM) per year, it is readily apparent that the costs for supplying and exhausting air through a wet bench are significant. For example, a 16 1 S00 CFM wet bench used two hours per day for 365 days a year can reduce its 17 exhaust by 30% when it is not in use. Using a conservative cost for both makeup and 18 exhaust scrubbing/VOC of $30 per CFM per year, the savings from a single wet 19 , bench would be about $12,375 per year.
Accordingly, it is a primary object of the present invention to provide 21 an improved air flow control apparatus for a semiconductor manufacturing wet bench 22 which significantly reduces the cost of operation of the wet bench by varying the 23 amount of air flow through the wet bench between high and low flow conditions 24 which are dictated by the nature of the activity that is occurring within the wet bench.
Another object of the present invention is to provide such an improved 26 apparatus which is adapted to reduce the flow of air through the interior of a wet 27 bench when conditions are such that fumes are not present and therefore a lower flow 28 can be utilized.
1 A related object is to provide such an improved apparatus which does 2 not jeopardize the safety of users working near wet benches, but by virtue of its 3 operation, can significantly reduce the costs associated with supplying air to and 4 exhausting air from the wet bench.
Still another object of the present invention is to provide an apparatus 6 for controlling the amount of flow of air through a wet bench, and which monitors the 7 actual flow of air being exhausted so that it can be accumulated and used for STC?
8 purposes.
9 An ancillary object lies in the provision of such data being available for transmission to the heating, ventilating and air conditioning system so that control of 11 the HVAC system can be done in a manner which takes into account the amount of 12 air that may be used by the wet benches.
13 Yet another object is to provide such an improved apparatus which is 14 adapted to detect degradation of the operation of the system for supplying air to and 1 S exhausting air from the wet bench and to provide notification of alarm conditions 16 immediately upon detection.
17 Still another object of the present invention is to provide such an 18 apparatus which has the capability of integrating its operation with that of a heating, 19 ventilating and air conditioning control system, and which can be controlled from a remote location, over a communication network.
21 These and other objects will become apparent upon reading the 22 following detailed description of the present invention, while referring to the attached 23 drawings, in which:
24 FIGURE 1 is a schematic block diagram of apparatus of the present invention installed on a wet bench;
26 FIG. 2 is a front view of an operator display panel that is part of the 27 apparatus shown in FIG. 1;
28 FIG. 3 is a flow chart illustrating the operation of a preferred 1 embodiment of the apparatus of the present invention;
2 FIG. 4 is a block diagram illustrating the relative positions of FIGS. 4a, 3 4b, 4c, 4d and 4e to one another, and which together comprise a schematic diagram 4 of the electrical circuitry for the controller portion of the apparatus embodying the present invention; and, 6 FIGS. 4a, 4b, 4c, 4d and 4e, which if connected together, comprise the 7 schematic diagram of the electrical circuitry for the wet bench controller means 8 embodying the present invention.
Broadly stated, the present invention is directed to an apparatus for 11 controlling the flow volume of air that is supplied to and exhausted from the interior 12 of an electronic manufacturing wet bench of the type which utilizes corrosive 13 chemicals, such as acids, to perform such manufacturing steps as etching wafers that 14 are being fabricated within the wet bench. The apparatus varies the flow depending upon whether corrosive acids are going to be introduced into the wet bench enclosure 16 or are being used therein, so that fumes within the wet bench enclosure are safely and 17 effectively exhausted.
18 While wet benches typically have enclosures, some do not. In the event 19 a wet bench does not have an enclosure, the exhaust duct is usually positioned in close proximity to the work area of the bench where acid is introduced so that fumes can 21 be exhausted from the work area while acid is present. The opening to the exhaust 22 duct is preferably very close to the acid retaining receptacle and the exhaust duct 23 extends through the interior of the bench and then to a duct manifold and air cleaning 24 equipment.
The wet benches are preferably exhausted by an exhaust system that 26 includes a single blower connected to the exhaust manifold that is in turn connected 27 to the individual ducts from multiple wet benches, and dampers may be provided in 1 the individual ducts to control the flow from the individual wet benches.
2 Alternatively, a blower associated with each duct that is capable of being driven at 3 variable speeds to increase or decrease the flow of air from the wet bench can be used, 4 but that alternative is most likely less cost effective if the flow is merely varied between high and low flow rates.
6 The apparatus of the present invention effectively varies the flow 7 between high flow and low flow operation although the invention is not limited to 8 such high/low flow variation and may be more than two flow levels or even a variable 9 flow operation. For purposes of description herein, the full speed or high flow operation will be referred to as normal operation, with the lower speed or low flow 11 condition being referred to as the setback speed. It should be understood that the 12 setback set point can be varied depending upon safety requirements that are dictated 13 by authorities of one form or another, but are preferably approximately 70%
of the 14 normal flow. The normal flow is generally considered to be the high flow condition and may be the maximum flow that can be produced by the system. However, it 16 should be understood that a purge or emergency condition may be implemented 17 wherein flow rates higher than the high flow or normal flow condition may be 18 produced. This could be achieved by increasing the speed of the blower that is used 19 to exhaust air from the wet benches through a manifold system wherein a duct is employed to exhaust fumes from the wet bench to a manifold and whereby the flow 21 through the duct is principally controlled by the apparatus of the present invention 22 utilizing a damper that is variably positioned between the high and low flow 23 producing positions.
24 In the preferred embodiment, the apparatus is a two position control which varies between a normal high flow operation and a setback, low flow operation 26 which is preferably approximately 70% of the high flow operation.
27 Turning now to the drawings and particularly FIG. 1, the apparatus of 28 the present invention is shown to include a wet bench, indicated generally at 10, 1 which has an access door 12 located in the front thereof through which users can 2 attend to manufacturing steps that take place within the wet bench 10. An exhaust 3 duct 14 is connected to the wet bench enclosure top 16 and duct 14 extends to an 4 exhaust manifold (not shown) to which other exhaust ducts from other wet benches may be connected and the manifold is in communication with a blower and other 6 equipment that is used to clean and exhaust air to atmosphere. Flow within the duct 7 14 is controlled by a pivotable damper 18 that is controlled by an actuator 20 that is 8 preferably a pneumatic damper actuator, but which may be of various other designs 9 including electrical actuators of various types.
The actuator 20 is controlled by an analog output pneumatic (AOP) 11 module 22 which has a supply air line 24 which supplies air at preferably 18 to 30 12 p.s.i. gauge pressure for use by the actuator 20. The AOP module 22 is controlled by 13 a multiconductor cable 26 that is connected to a controller 28 that is self contained 14 and preferably installed near the wet bench. The controller 28 includes the circuitry shown in FIGS. 4a-4e and controls the operation of the apparatus as established by 16 control algorithms together with user input information that is supplied by an operator 17 display panel 30 that is mounted to the front of the wet bench 10.
18 The operator display panel is shown in FIG. 2 and includes a display 32 19 that is preferably a liquid crystal display that during operation preferably continuously displays the operating air flow in cubic feet per minute. The display shown in FIG.
21 2 indicates the flow is zero and that the apparatus is not in operation.
The display 22 panel includes a preferably green status light 34, preferably an LED, which indicates 23 normal operation, a similar light 36, preferably yellow and indicating a warning 24 condition and another light 3 8 which is preferably red and indicates an alarm condition. The display panel includes an emergency purge pushbutton switch 40 with 26 associated indicating light 42, an alarm silence pushbutton 44 and associate indicating 27 light 46 and a pushbutton 48 and associated light SO which can be used to replace the 28 present flow with the alternate flow, i.e., to switch from high to low or low to high 1 flow operation. The display 32 also has the capability of displaying the letters EEE
2 for emergency mode and FFF for fail mode.
3 Returning to FIG. 1, the apparatus includes an air flow sensor 52 that 4 is located within the exhaust duct 14 and it is connected to a differential pressure transmitter 54 that is connected as an input to the controller 28 via line 56.
Line 58 6 is connected to a 24 VAC power source and multiconductor line 60 connects the 7 controller 28 to the operator display panel 30. The display panel also includes an 8 audio alarm horn, although a separate audio alarm can be mounted elsewhere in the 9 area or on the wet bench itself.
Broadly stated, the controller provides high and low flow operation with 11 the high flow set point determining the flow rate when the wet bench is in use and a 12 low flow or setback set point when it is not in use. Alarming is based on 13 measurement of the actual flow as determined by the flow sensor 52 compared to the 14 set point. The selection of the high or low flow set point can be done in several ways, including a manually selected value from the user interface, i.e., the switch 48 on the 16 operator display panel. A second way in which the set point can be set high or low 17 is for an input line 64 be connected to a sensor 66 which provides a digital input 18 signal indicating the detection of acid in the tank for triggering the high flow 19 operation. Another way to trigger the high flow condition is to interconnect the controller via the input DI1 with the wet bench control system itself which would 21 switch the controller to a high flow condition when the wet bench system is activated 22 to fill its tank with acid. Such an input signal preferably initiates an internal timer 23 within the controller 28 which is preferably set to time out a safe period of time after 24 the acid has been purged from the system which then results in the switching to the low flow or setback mode of operation.
26 From an operator or user standpoint, the controller 28 monitors the 27 status of the wet bench during operation. Once the apparatus detects an operator's 28 intent to use the equipment, it reacts in less than one second to change the exhaust 1 flow from a setback flow to normal or full flow operation. During this process, the 2 display panel indicates in CFM the actual flow through the wet bench and status lights 3 will show normal (preferably green), marginal (preferably yellow), or alarm 4 (preferably red) conditions. An audible alarm can be enabled to indicate a low flow or red condition. The alarm can also be activated to announce when the purge button 6 has been pushed. The purge button 40 can be pushed at any time which opens the 7 control damper 18 to its full open position such as might be required if the operator 8 encounters a spill or other unsafe condition. The operator can manually set the flow 9 from low or high flow conditions to the reverse. Once the wet bench is out of service or the apparatus indicates that it is no longer being used, a time delay can be set to 11 reduce the exhaust flow to its setback set point. The operator is afforded for safety 12 by knowing that what the actual flow in CFM is through the displaying of this 13 information at the display panel and has the ability to increase or decrease flow or 14 perform an emergency purge while he is present at the wet bench location.
1 S Turning now to FIG. 3 which is a flow chart illustrating the operation 16 of the apparatus of the present invention, the control algorithm is shown to start 17 (block 70) wherein a determination is made whether start has been initialized (block 18 72). If it has, then the apparatus changes to the high or normal set point (block 74) 19 and if not, it sets the set point to the low flow or setback value (block 76). If it has changed to the high set point, it inquires whether purge has been initialized (block 21 78), which if not, merely checks for alarms (block 80) as is the case after the low flow 22 set point has been set. If a purge has been initialized, then a timer is initiated or set 23 (block 82). The amount of time before the timer times out is adjustable between zero 24 and approximately 25 minutes, but can be a greater or smaller time period if desired.
Once the timer times out, it switches the apparatus to the low flow set point (block 84) 26 and thereafter checks for alarms. The checking for alarms is accomplished by 27 inquiring as to whether the flow is too high (block 86), which if not, results in a 28 determination as to whether the flow is too low (block 88). If it is neither too high nor 1 too low, the algorithm returns to start block 90. If the flow is too high, it activates the 2 red alarm 38 (block 92) and if the flaw is too low, it also does the same (block 94).
3 Referring to the composite electrical schematic diagram of the circuitry 4 of the wet bench controller, if the separate drawings FIGS. 4a, 4b, 4c, 4d and 4e are S placed adjacent one another in the manner shown in FIG. 4, the total electrical 6 schematic diagram of the wet bench controller 20 is illustrated. The operation of the 7 circuitry of FIGS. 4a through 4e will not be described in detail. The circuitry is 8 driven by a microprocessor and the important algorithms that carry out the control 9 functions of the controller will be hereinafter described. Referring to FIG.
4c, the ~rht circuitry includes a Motorola MC; 68HC1 I microprocessor 1'ZO which is clocked at 1 I 8 MHZ by a crystal 122. 3Me microprocessor 120 has a databus 124 that is connected 12 to a tri-state buffer 126 (FIG. 4d) which in turn is connected to an electrically 13 programmable read only memory I28 that is also connected to the databus 124. The 14 EPROM 128 has address lines AO through A7 connected to the tri-state buffer and also has address lines A8 through A14 connected to the microprocessor 120.
I 6 The circuitry includes a 3 to 8-bit multiplexer 130, a data latch 132 (see 17 FIG. 4d), a digital-to-analog converter 134, which is adapted to provide the analog 18 outputs indicative of the volume of air being exhausted by the wet bench, which 19 information may be provided to the HVAC control system. Referring to FIG.
4b, an RS232 driver 136 is provided for transmitting and receiving information through a 21 hand held terminal (not shown). The other components are well known and therefore 22 need not be otherwise described.
23 One of the significant advantages of the present invention is that the 24 controller executes its control scheme; in a repetitive and extremely rapid manner.
The microprocessor samples flow signal information as well as sash door position 26 signals at a speed of approximately one sample per 100 milliseconds during operation.
27 'rhe result is that rapid responsive control action is accomplished as is desired.
28 From the foregoing, it should be understood that apparatus embodying 1 the present invention has been shown and described which effectively controls the 2 flow of air through a semiconductor manufacturing wet bench of the type which 3 utilizes corrosive or dangerous chemicals such as acids and the like for performing 4 various steps during the manufacture of such semiconductors. The control of the flow is advantageous in that it assures safe operation of the wet bench and safety for the 6 users working in the area. However, the apparatus additionally reduces the amount 7 of air that is exhausted from the interior of the wet bench during those times where 8 the chemicals or acids are not being used and thereby reduces the amount of make-up 9 or replacement air that must be supplied to the wet bench enclosure and also reduces the amount of air that must be cleaned after it is removed from the wet bench before 11 it can be vented to atmosphere. Since the air that is supplied to the wet bench must 12 be of clean room quality and which involves considerable expense, the operating costs 13 for a wet bench can be significantly reduced.
14 While various embodiments of the present invention have been shown and described, it should be understood that various alternatives, substitutions and 16 equivalents can be used, and the present invention should only be limited by the 17 claims and equivalents thereof.
18 Various features of the present invention are set forth in the following 19 claims.
8 Manufacturing stations for manufacturing many types of electronic 9 semiconductor products are known in the electronic industry as wet benches.
A wet bench is a process equipment tool that is used to etch semiconductor wafers during 11 the manufacturing of them. The etching is done by acids that are inherently 12 dangerous to individuals that may be present in the area, and for that reason, the acid 13 fumes must be expelled during and after use of the acid during the manufacturing 14 process. The wet benches generally have an enclosure which has an access door for users, and the enclosure is typically connected to an exhaust system for removing the 16 noxious fumes so that the users will not be exposed to them.
17 Wet benches are typically used intermittently throughout a work day.
18 Each time they are used, a tank associated with the wet bench is filled with acid, 19 which is then expelled after the semiconductotr wafers are etched. During the filling and use of the acid, the fumes produced must be exhausted to prevent any contact 21 with users. Manufacturers of semiconductors are generally not concerned with the 22 amount of flow of air that is moved through the interior of the wet bench enclosures, 1 and the flow is generally constant regardless of the presence or impounding presence 2 of acid being introduced or when the wet bench is idle.
3 The volume of air that is moved through a wet bench can significantly 4 impact on the cost of operating the wet bench. Since the replacement air that is S introduced into the wet bench must be clean room quality air, it has to be processed 6 and filtered to remove any particles that could otherwise contaminate the 7 semiconductor wafers during their manufacture. It is also necessary to condition the 8 air with respect to its temperature and humidity and there are also costs associated 9 with such conditioning. Also, exhausted air from the wet bench must have acid fumes removed from the exhaust before the air can be vented to atmosphere.
11 With respect to the costs associated with operation of a wet bench, clean 12 room replacement air can cost as high as $50-$60 per cubic foot per minute per year 13 as well as additional scrubbing for EOC incineration costs which can range from $30-14 $150 per cubic foot per minute (CFM) per year, it is readily apparent that the costs for supplying and exhausting air through a wet bench are significant. For example, a 16 1 S00 CFM wet bench used two hours per day for 365 days a year can reduce its 17 exhaust by 30% when it is not in use. Using a conservative cost for both makeup and 18 exhaust scrubbing/VOC of $30 per CFM per year, the savings from a single wet 19 , bench would be about $12,375 per year.
Accordingly, it is a primary object of the present invention to provide 21 an improved air flow control apparatus for a semiconductor manufacturing wet bench 22 which significantly reduces the cost of operation of the wet bench by varying the 23 amount of air flow through the wet bench between high and low flow conditions 24 which are dictated by the nature of the activity that is occurring within the wet bench.
Another object of the present invention is to provide such an improved 26 apparatus which is adapted to reduce the flow of air through the interior of a wet 27 bench when conditions are such that fumes are not present and therefore a lower flow 28 can be utilized.
1 A related object is to provide such an improved apparatus which does 2 not jeopardize the safety of users working near wet benches, but by virtue of its 3 operation, can significantly reduce the costs associated with supplying air to and 4 exhausting air from the wet bench.
Still another object of the present invention is to provide an apparatus 6 for controlling the amount of flow of air through a wet bench, and which monitors the 7 actual flow of air being exhausted so that it can be accumulated and used for STC?
8 purposes.
9 An ancillary object lies in the provision of such data being available for transmission to the heating, ventilating and air conditioning system so that control of 11 the HVAC system can be done in a manner which takes into account the amount of 12 air that may be used by the wet benches.
13 Yet another object is to provide such an improved apparatus which is 14 adapted to detect degradation of the operation of the system for supplying air to and 1 S exhausting air from the wet bench and to provide notification of alarm conditions 16 immediately upon detection.
17 Still another object of the present invention is to provide such an 18 apparatus which has the capability of integrating its operation with that of a heating, 19 ventilating and air conditioning control system, and which can be controlled from a remote location, over a communication network.
21 These and other objects will become apparent upon reading the 22 following detailed description of the present invention, while referring to the attached 23 drawings, in which:
24 FIGURE 1 is a schematic block diagram of apparatus of the present invention installed on a wet bench;
26 FIG. 2 is a front view of an operator display panel that is part of the 27 apparatus shown in FIG. 1;
28 FIG. 3 is a flow chart illustrating the operation of a preferred 1 embodiment of the apparatus of the present invention;
2 FIG. 4 is a block diagram illustrating the relative positions of FIGS. 4a, 3 4b, 4c, 4d and 4e to one another, and which together comprise a schematic diagram 4 of the electrical circuitry for the controller portion of the apparatus embodying the present invention; and, 6 FIGS. 4a, 4b, 4c, 4d and 4e, which if connected together, comprise the 7 schematic diagram of the electrical circuitry for the wet bench controller means 8 embodying the present invention.
Broadly stated, the present invention is directed to an apparatus for 11 controlling the flow volume of air that is supplied to and exhausted from the interior 12 of an electronic manufacturing wet bench of the type which utilizes corrosive 13 chemicals, such as acids, to perform such manufacturing steps as etching wafers that 14 are being fabricated within the wet bench. The apparatus varies the flow depending upon whether corrosive acids are going to be introduced into the wet bench enclosure 16 or are being used therein, so that fumes within the wet bench enclosure are safely and 17 effectively exhausted.
18 While wet benches typically have enclosures, some do not. In the event 19 a wet bench does not have an enclosure, the exhaust duct is usually positioned in close proximity to the work area of the bench where acid is introduced so that fumes can 21 be exhausted from the work area while acid is present. The opening to the exhaust 22 duct is preferably very close to the acid retaining receptacle and the exhaust duct 23 extends through the interior of the bench and then to a duct manifold and air cleaning 24 equipment.
The wet benches are preferably exhausted by an exhaust system that 26 includes a single blower connected to the exhaust manifold that is in turn connected 27 to the individual ducts from multiple wet benches, and dampers may be provided in 1 the individual ducts to control the flow from the individual wet benches.
2 Alternatively, a blower associated with each duct that is capable of being driven at 3 variable speeds to increase or decrease the flow of air from the wet bench can be used, 4 but that alternative is most likely less cost effective if the flow is merely varied between high and low flow rates.
6 The apparatus of the present invention effectively varies the flow 7 between high flow and low flow operation although the invention is not limited to 8 such high/low flow variation and may be more than two flow levels or even a variable 9 flow operation. For purposes of description herein, the full speed or high flow operation will be referred to as normal operation, with the lower speed or low flow 11 condition being referred to as the setback speed. It should be understood that the 12 setback set point can be varied depending upon safety requirements that are dictated 13 by authorities of one form or another, but are preferably approximately 70%
of the 14 normal flow. The normal flow is generally considered to be the high flow condition and may be the maximum flow that can be produced by the system. However, it 16 should be understood that a purge or emergency condition may be implemented 17 wherein flow rates higher than the high flow or normal flow condition may be 18 produced. This could be achieved by increasing the speed of the blower that is used 19 to exhaust air from the wet benches through a manifold system wherein a duct is employed to exhaust fumes from the wet bench to a manifold and whereby the flow 21 through the duct is principally controlled by the apparatus of the present invention 22 utilizing a damper that is variably positioned between the high and low flow 23 producing positions.
24 In the preferred embodiment, the apparatus is a two position control which varies between a normal high flow operation and a setback, low flow operation 26 which is preferably approximately 70% of the high flow operation.
27 Turning now to the drawings and particularly FIG. 1, the apparatus of 28 the present invention is shown to include a wet bench, indicated generally at 10, 1 which has an access door 12 located in the front thereof through which users can 2 attend to manufacturing steps that take place within the wet bench 10. An exhaust 3 duct 14 is connected to the wet bench enclosure top 16 and duct 14 extends to an 4 exhaust manifold (not shown) to which other exhaust ducts from other wet benches may be connected and the manifold is in communication with a blower and other 6 equipment that is used to clean and exhaust air to atmosphere. Flow within the duct 7 14 is controlled by a pivotable damper 18 that is controlled by an actuator 20 that is 8 preferably a pneumatic damper actuator, but which may be of various other designs 9 including electrical actuators of various types.
The actuator 20 is controlled by an analog output pneumatic (AOP) 11 module 22 which has a supply air line 24 which supplies air at preferably 18 to 30 12 p.s.i. gauge pressure for use by the actuator 20. The AOP module 22 is controlled by 13 a multiconductor cable 26 that is connected to a controller 28 that is self contained 14 and preferably installed near the wet bench. The controller 28 includes the circuitry shown in FIGS. 4a-4e and controls the operation of the apparatus as established by 16 control algorithms together with user input information that is supplied by an operator 17 display panel 30 that is mounted to the front of the wet bench 10.
18 The operator display panel is shown in FIG. 2 and includes a display 32 19 that is preferably a liquid crystal display that during operation preferably continuously displays the operating air flow in cubic feet per minute. The display shown in FIG.
21 2 indicates the flow is zero and that the apparatus is not in operation.
The display 22 panel includes a preferably green status light 34, preferably an LED, which indicates 23 normal operation, a similar light 36, preferably yellow and indicating a warning 24 condition and another light 3 8 which is preferably red and indicates an alarm condition. The display panel includes an emergency purge pushbutton switch 40 with 26 associated indicating light 42, an alarm silence pushbutton 44 and associate indicating 27 light 46 and a pushbutton 48 and associated light SO which can be used to replace the 28 present flow with the alternate flow, i.e., to switch from high to low or low to high 1 flow operation. The display 32 also has the capability of displaying the letters EEE
2 for emergency mode and FFF for fail mode.
3 Returning to FIG. 1, the apparatus includes an air flow sensor 52 that 4 is located within the exhaust duct 14 and it is connected to a differential pressure transmitter 54 that is connected as an input to the controller 28 via line 56.
Line 58 6 is connected to a 24 VAC power source and multiconductor line 60 connects the 7 controller 28 to the operator display panel 30. The display panel also includes an 8 audio alarm horn, although a separate audio alarm can be mounted elsewhere in the 9 area or on the wet bench itself.
Broadly stated, the controller provides high and low flow operation with 11 the high flow set point determining the flow rate when the wet bench is in use and a 12 low flow or setback set point when it is not in use. Alarming is based on 13 measurement of the actual flow as determined by the flow sensor 52 compared to the 14 set point. The selection of the high or low flow set point can be done in several ways, including a manually selected value from the user interface, i.e., the switch 48 on the 16 operator display panel. A second way in which the set point can be set high or low 17 is for an input line 64 be connected to a sensor 66 which provides a digital input 18 signal indicating the detection of acid in the tank for triggering the high flow 19 operation. Another way to trigger the high flow condition is to interconnect the controller via the input DI1 with the wet bench control system itself which would 21 switch the controller to a high flow condition when the wet bench system is activated 22 to fill its tank with acid. Such an input signal preferably initiates an internal timer 23 within the controller 28 which is preferably set to time out a safe period of time after 24 the acid has been purged from the system which then results in the switching to the low flow or setback mode of operation.
26 From an operator or user standpoint, the controller 28 monitors the 27 status of the wet bench during operation. Once the apparatus detects an operator's 28 intent to use the equipment, it reacts in less than one second to change the exhaust 1 flow from a setback flow to normal or full flow operation. During this process, the 2 display panel indicates in CFM the actual flow through the wet bench and status lights 3 will show normal (preferably green), marginal (preferably yellow), or alarm 4 (preferably red) conditions. An audible alarm can be enabled to indicate a low flow or red condition. The alarm can also be activated to announce when the purge button 6 has been pushed. The purge button 40 can be pushed at any time which opens the 7 control damper 18 to its full open position such as might be required if the operator 8 encounters a spill or other unsafe condition. The operator can manually set the flow 9 from low or high flow conditions to the reverse. Once the wet bench is out of service or the apparatus indicates that it is no longer being used, a time delay can be set to 11 reduce the exhaust flow to its setback set point. The operator is afforded for safety 12 by knowing that what the actual flow in CFM is through the displaying of this 13 information at the display panel and has the ability to increase or decrease flow or 14 perform an emergency purge while he is present at the wet bench location.
1 S Turning now to FIG. 3 which is a flow chart illustrating the operation 16 of the apparatus of the present invention, the control algorithm is shown to start 17 (block 70) wherein a determination is made whether start has been initialized (block 18 72). If it has, then the apparatus changes to the high or normal set point (block 74) 19 and if not, it sets the set point to the low flow or setback value (block 76). If it has changed to the high set point, it inquires whether purge has been initialized (block 21 78), which if not, merely checks for alarms (block 80) as is the case after the low flow 22 set point has been set. If a purge has been initialized, then a timer is initiated or set 23 (block 82). The amount of time before the timer times out is adjustable between zero 24 and approximately 25 minutes, but can be a greater or smaller time period if desired.
Once the timer times out, it switches the apparatus to the low flow set point (block 84) 26 and thereafter checks for alarms. The checking for alarms is accomplished by 27 inquiring as to whether the flow is too high (block 86), which if not, results in a 28 determination as to whether the flow is too low (block 88). If it is neither too high nor 1 too low, the algorithm returns to start block 90. If the flow is too high, it activates the 2 red alarm 38 (block 92) and if the flaw is too low, it also does the same (block 94).
3 Referring to the composite electrical schematic diagram of the circuitry 4 of the wet bench controller, if the separate drawings FIGS. 4a, 4b, 4c, 4d and 4e are S placed adjacent one another in the manner shown in FIG. 4, the total electrical 6 schematic diagram of the wet bench controller 20 is illustrated. The operation of the 7 circuitry of FIGS. 4a through 4e will not be described in detail. The circuitry is 8 driven by a microprocessor and the important algorithms that carry out the control 9 functions of the controller will be hereinafter described. Referring to FIG.
4c, the ~rht circuitry includes a Motorola MC; 68HC1 I microprocessor 1'ZO which is clocked at 1 I 8 MHZ by a crystal 122. 3Me microprocessor 120 has a databus 124 that is connected 12 to a tri-state buffer 126 (FIG. 4d) which in turn is connected to an electrically 13 programmable read only memory I28 that is also connected to the databus 124. The 14 EPROM 128 has address lines AO through A7 connected to the tri-state buffer and also has address lines A8 through A14 connected to the microprocessor 120.
I 6 The circuitry includes a 3 to 8-bit multiplexer 130, a data latch 132 (see 17 FIG. 4d), a digital-to-analog converter 134, which is adapted to provide the analog 18 outputs indicative of the volume of air being exhausted by the wet bench, which 19 information may be provided to the HVAC control system. Referring to FIG.
4b, an RS232 driver 136 is provided for transmitting and receiving information through a 21 hand held terminal (not shown). The other components are well known and therefore 22 need not be otherwise described.
23 One of the significant advantages of the present invention is that the 24 controller executes its control scheme; in a repetitive and extremely rapid manner.
The microprocessor samples flow signal information as well as sash door position 26 signals at a speed of approximately one sample per 100 milliseconds during operation.
27 'rhe result is that rapid responsive control action is accomplished as is desired.
28 From the foregoing, it should be understood that apparatus embodying 1 the present invention has been shown and described which effectively controls the 2 flow of air through a semiconductor manufacturing wet bench of the type which 3 utilizes corrosive or dangerous chemicals such as acids and the like for performing 4 various steps during the manufacture of such semiconductors. The control of the flow is advantageous in that it assures safe operation of the wet bench and safety for the 6 users working in the area. However, the apparatus additionally reduces the amount 7 of air that is exhausted from the interior of the wet bench during those times where 8 the chemicals or acids are not being used and thereby reduces the amount of make-up 9 or replacement air that must be supplied to the wet bench enclosure and also reduces the amount of air that must be cleaned after it is removed from the wet bench before 11 it can be vented to atmosphere. Since the air that is supplied to the wet bench must 12 be of clean room quality and which involves considerable expense, the operating costs 13 for a wet bench can be significantly reduced.
14 While various embodiments of the present invention have been shown and described, it should be understood that various alternatives, substitutions and 16 equivalents can be used, and the present invention should only be limited by the 17 claims and equivalents thereof.
18 Various features of the present invention are set forth in the following 19 claims.
Claims (21)
1. An apparatus for controlling air flow through a wet bench that uses corrosive chemicals for semiconductor manufacture and that has a duct for carrying air away from a work area of the wet bench and means for exhausting air from the work area through the duct, the apparatus comprising:
means for indicating operation in any one of a plurality of operational modes, the plurality of operational modes comprising a first operational mode wherein corrosive chemicals will be introduced into the work area; and means for setting a rate of air flow through the duct at a first predetermined flow rate in response to indications from the indicating means of operation in the first operational mode.
means for indicating operation in any one of a plurality of operational modes, the plurality of operational modes comprising a first operational mode wherein corrosive chemicals will be introduced into the work area; and means for setting a rate of air flow through the duct at a first predetermined flow rate in response to indications from the indicating means of operation in the first operational mode.
2. An apparatus according to claim 1 wherein the indicating means comprises means for detecting a presence of corrosive chemicals in the work area.
3. An apparatus according to claim 1 comprising a controller for operating the wet bench, the controller configured to issue an operating signal at a time before corrosive chemicals are to be introduced into the work area and wherein, in response to the operational signal, the indicating means generates an indication of operation in the first operational mode.
4. An apparatus according to claim 3 wherein the indicating means removes the indication of operation in the first operational mode after expiration of a predetermined time period.
5. An apparatus according to claim 2 wherein the setting means comprises a damper means, the damper means located in the duct.
6. An apparatus according to claim 1 comprising a controller means, the controller means operatively connected to the indicating means and the controller means configured to generate signals for controlling the setting means.
7. An apparatus according to claim 6 wherein the setting means comprises means for sensing the rate of air flow through the duct.
8. An apparatus for controlling air flow through a wet bench that uses corrosive chemicals for semiconductor manufacture and that has an opening for supplying air to a work area of the wet bench, a duct for carrying air away from the work area and means for exhausting air from the work area through the duct, the apparatus comprising:
means for indicating operation in either one of a high flow operational mode and a low flow operational mode in response to presence and absence of an indication of impending introduction and use of corrosive chemicals within the wet bench;
a controller means connected to receive indications from the indicating means and configured to generate a high flow control signal in response to indications of operation in the high flow operational mode and to generate a low flow control signal in response to indications of operation in the low flow operational mode; and means for varying a rate of air flow through the duct, the varying means connected to receive flow control signals from the controller means, the varying means operative to vary the rate of air flow between at least a high flow rate in response to receiving the high flow control signal and a low flow rate in response to receiving the low flow control signal.
means for indicating operation in either one of a high flow operational mode and a low flow operational mode in response to presence and absence of an indication of impending introduction and use of corrosive chemicals within the wet bench;
a controller means connected to receive indications from the indicating means and configured to generate a high flow control signal in response to indications of operation in the high flow operational mode and to generate a low flow control signal in response to indications of operation in the low flow operational mode; and means for varying a rate of air flow through the duct, the varying means connected to receive flow control signals from the controller means, the varying means operative to vary the rate of air flow between at least a high flow rate in response to receiving the high flow control signal and a low flow rate in response to receiving the low flow control signal.
9. An apparatus according to claim 8 comprising a flow sensing means located in the duct for determining a measured rate of air flow through the duct, the flow sensing means connected to supply the controller means with a signal indicative of the measured rate of air flow.
10. An apparatus according to claim 9 comprising a display means connected to the controller means, the display means configured to display the measured rate of air flow through the duct.
11. An apparatus according to claim 10 wherein the indicating means comprises means for detecting a presence of corrosive chemicals in the work area and wherein, in response to detection of corrosive chemicals in the work area, the indicating means provides an indication of operation in the high flow operational mode.
12. An apparatus according to claim 10 wherein, in response to receipt of a signal indicating that corrosive chemicals will be introduced into the work area, the indicating means provides an indication of operation in the high flow operational mode.
13. An apparatus according to claim 10 wherein the display means comprises an emergency purge switch and wherein, in response to activation of the emergency purge switch, the indicating means provides an indication of operation in the high flow operational mode.
14. An apparatus according to claim 10 wherein the display means is configured to display status information relating to operation of the apparatus, the status information including one or more of: a normal condition, a warning condition and an alarm condition.
15. An apparatus according to claim 14 wherein the status information comprises a green indicator for the normal condition, a yellow indicator for the warning condition and a red indicator for the alarm condition.
16. An apparatus according to claim 10 wherein the display means comprises a switch for selecting between the high flow and low flow operational modes.
17. An apparatus according to claim 10 wherein the display means comprises an audio alarm and a switch for silencing the audio alarm.
18. An apparatus according to claim 9 wherein, when the indicating means indicates operation in the high flow operational mode, the controller means is configured to compare the measured rate of air flow to a predetermined high flow rate set point and to generate a warning signal if the measured rate of air flow varies from the predetermined high flow rate set point by more than a first predetermined amount and wherein, when the indicating means indicates operation in the low flow operational mode, the controller means is configured to compare the measured rate of air flow to a predetermined low flow rate set point and to generate the warning signal if the measured rate of air flow varies from the predetermined low flow rate set point by more than the first predetermined amount.
19. An apparatus according to claim 18 wherein, when the indicating means indicates operation in the high flow operational mode, the controller means is configured to compare the measured rate of air flow to the predetermined high flow rate set point and to generate an alarm signal if the measured rate of air flow varies from the predetermined high flow rate set point by more than a second predetermined amount that is greater than the first predetermined amount and wherein, when the indicating means indicates operation in the low flow operational mode, the controller means is configured to compare the measured rate of air flow to the predetermined low flow rate set point and to generate the alarm signal if the measured rate of air flow varies from the predetermined low flow rate set point by more than the second predetermined amount.
20. An apparatus according to claim 8 wherein the varying means comprises a damper means, the damper means located in the duct.
21. An apparatus according to claim 10 wherein the display means comprises an emergency purge switch and wherein, in response to activation of the emergency purge switch, the indicating means provides an indication of operation in an emergency flow operational mode, the controller means generates an emergency flow control signal and the varying means increases the rate of air flow through the duct to an emergency flow rate that is greater than the high flow rate.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US09/247,698 US6152818A (en) | 1999-02-10 | 1999-02-10 | Flow control apparatus for a semiconductor manufacturing wet bench |
| US09/247,698 | 1999-02-10 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2290922A1 CA2290922A1 (en) | 2000-08-10 |
| CA2290922C true CA2290922C (en) | 2005-02-22 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002290922A Expired - Lifetime CA2290922C (en) | 1999-02-10 | 1999-11-29 | Flow control apparatus for a semiconductor manufacturing wet bench |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US6152818A (en) |
| CA (1) | CA2290922C (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6577914B1 (en) * | 1999-08-10 | 2003-06-10 | Advanced Micro Devices, Inc. | Method and apparatus for dynamic model building based on machine disturbances for run-to-run control of semiconductor devices |
| DE10316571A1 (en) * | 2003-04-10 | 2004-10-28 | BSH Bosch und Siemens Hausgeräte GmbH | Control device for an extractor hood |
| US20110279265A1 (en) * | 2010-05-11 | 2011-11-17 | Kewaunee Scientific Corporation | System for displaying information related to an operational parameter of a biological safety cabinet |
| SE537339C2 (en) * | 2012-06-25 | 2015-04-07 | Medicvent Ab | A central flow system |
| US10056276B2 (en) | 2014-12-22 | 2018-08-21 | Wafertech, Llc | Fluid monitoring system and method for semiconductor fabrication tools |
| PL3306217T3 (en) * | 2016-10-04 | 2020-10-19 | Lindinvent Ab | Supply air device for controlling supply air flow |
Family Cites Families (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3752056A (en) * | 1970-11-04 | 1973-08-14 | Sheldon And Co E | Laboratory exhaust hood |
| US3728866A (en) * | 1971-07-08 | 1973-04-24 | Interlab Inc | Exhaustless clean room work stations |
| US3811250A (en) * | 1971-12-15 | 1974-05-21 | Becton Dickinson Co | Contamination control apparatus |
| US4377969A (en) * | 1980-12-08 | 1983-03-29 | Kewaunee Scientific Equipment Corp. | Automatic fume hood airflow control |
| US4466454A (en) * | 1982-11-23 | 1984-08-21 | Interlab, Inc. | Automated work transfer system |
| US4528898A (en) * | 1984-03-05 | 1985-07-16 | Imec Corporation | Fume hood controller |
| JPS63248449A (en) * | 1987-04-03 | 1988-10-14 | Tadahiro Omi | Draft chamber |
| US4982605A (en) * | 1989-05-17 | 1991-01-08 | Alnor Instrument Company | Air flow monitor and temperature compensating circuit therefor |
| US5401212A (en) * | 1990-08-29 | 1995-03-28 | Intelligent Enclosures Corporation | Environmental control system |
| US5170673A (en) * | 1990-09-28 | 1992-12-15 | Landis & Gyr Powers, Inc. | Method and apparatus for determining the uncovered size of an opening adapted to be covered by multiple moveable doors |
| US5240455A (en) * | 1991-08-23 | 1993-08-31 | Phoenix Controls Corporation | Method and apparatus for controlling a fume hood |
| US5470275A (en) * | 1993-04-05 | 1995-11-28 | Landis & Gyr Powers, Inc. | Method and apparatus for controlling fume hood face velocity using variable by-pass resistance |
| US5435779A (en) * | 1993-07-02 | 1995-07-25 | Phoenix Controls Corporation | Precision gas flow control by use of coarse and fine control elements |
| US5518446A (en) * | 1994-07-28 | 1996-05-21 | Landis & Gyr Powers, Inc. | Fume hood exhaust terminal |
| US5810657A (en) * | 1994-11-22 | 1998-09-22 | Lighthouse Associates, Inc. | Controller to maintain a certain set of environmental parameters in an environment |
| US5562537A (en) * | 1995-05-11 | 1996-10-08 | Landis & Gyr Powers, Inc. | Networked fume hood monitoring system |
| US5733188A (en) * | 1996-08-12 | 1998-03-31 | Landis & Staefa, Inc. | Speed of laboratory fume hood sash opening monitor and indicator |
| US5990789A (en) * | 1997-07-24 | 1999-11-23 | Lsi Logic Corporation | System and method for preventing smoke and fire damage to people and equipment in a clean room area from a fire |
-
1999
- 1999-02-10 US US09/247,698 patent/US6152818A/en not_active Expired - Lifetime
- 1999-11-29 CA CA002290922A patent/CA2290922C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| US6152818A (en) | 2000-11-28 |
| CA2290922A1 (en) | 2000-08-10 |
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