Abstract:
A method of accessing and cleaning an interior portion of a gas scrubber canister in-situ. A removable glass member is attachable to a flange formed on the canister. By removing the removable glass member an access port in communication with the interior portion of the canister is provided. A vacuum device is insertable through the access port to clean the interior portion in-situ.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is related to patent application Ser. No. 09/479,496, now U.S. Pat. No. 6,450,682, patent application Ser. No. 09/479,502, now abandoned; and patent application Ser. No. 09/479,428, now abandoned, all filed Jan. 7, 2000. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure relates to gas purifiers and more particularly to packed resin or dry chemical bed gas scrubber systems for the treatment of effluent gases produced in semiconductor manufacturing. 
     BACKGROUND OF THE INVENTION 
     In the fabrication of semiconductor devices toxic and corrosive gases, including halogenated species, are used in both etch and deposition processes. After use in a process chamber, the effluent gas stream must be treated before being exhausted into the environment. Several scrubbing devices attachable to an exhaust of the process chamber are known in the art. 
     Known scrubbing devices consist generally of three types; those which bumn the flammable components of the effluent gas stream, those which decompose water soluble components of the effluent stream in a wetting method and those which adsorb toxic components using adsorbents to chemically and physically decompose the toxic components. Stand-alone scrubbers of the adsorptive type must be periodically replaced as the adsorbent material is used in adsorbing the toxic components and as the adsorbent becomes deactivated with the by-products of reactions between the adsorbent and toxic compounds. 
     Additionally, particles formed as a by-product of the reactions between the adsorbent and toxic compounds accumulate in the scrubbing devices adversely affecting the flow of effluent gases therethrough. Known scrubbing devices do not provide for insitu cleaning and require that the device be taken off-line for such maintenance. 
     There therefore exists a need for a stand-alone scrubber system of the packed resin or dry chemical bed type which provides for in-situ cleaning thereof to remove accumulated particles. 
     SUMMARY OF THE INVENTION 
     A packed resin or dry chemical bed scrubber system and method for the treatment of effluent gases produced in semiconductor manufacturing is disclosed. In a preferred embodiment, the system includes a packed resin or dry chemical bed having a first resin or dry chemical layer packed between two layers of a second resin or dry chemical. A bottom screen and a top screen are provided for supporting the packed resin or dry chemical bed within a canister and to provide a substantially laminar flow of the effluent gases through the packed resin or dry chemical bed. A removable sight glass is provided for monitoring a bottom plenum of a canister in which the packed bed is disposed. The removable sight glass includes a glass member attachable to a flange formed in such manner that an access port is formed upon removal of the glass member. Access to the bottom plenum is thereby provided for in-situ cleaning of the bottom plenum, a dispersion nozzle and a first screen as further described herein. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The present disclosure will be better understood when consideration is given to the following detailed description. Such description makes reference to the annexed drawings, wherein: 
     FIG. 1 is a side elevation view of a canister in accordance with a disclosed embodiment; 
     FIG. 2 is a table showing representative reactions of the first resin or dry chemical material; 
     FIG. 3 is a table showing representative reactions of the second resin or dry chemical material; 
     FIG. 4 is a table showing exemplary temperature readings as the exothermic wavefront traverses the packed resin or dry chemical bed; 
     FIG. 5 is a partial cross sectional view of the dispersion nozzle; 
     FIG. 6 is an end view of the end portion of the dispersion nozzle; 
     FIG. 7 is a side elevation view of the dome; 
     FIG. 8 is a top plan view of a screen; 
     FIG. 9 is a partial cross sectional view of the sight glass; 
     FIG. 10 is a bottom plan view of the canister; and 
     FIG. 11 is a schematic view showing an in-situ cleaning of the bottom plenum. 
    
    
     DETAILED DESCRIPTION 
     An end of life prediction system disclosed herein uses the uniform movement of an exothermal wavefront through a resin or dry chemical bed typically maintained at ambient temperature (e.g. about 25° C.). To achieve this uniform movement, a packed bed canister, generally designated  10  in FIG. 1, includes the packed resin or dry chemical bed generally designated  20  and components and features that urge an upward laminar flow of effluent gases from a semiconductor fabrication tool through the canister  10 . As will be appreciated by those skilled in the art, a number of resins or dry chemicals may be used in the disclosed scrubber system depending upon the application and other factors. The described resins or dry chemicals should therefore be considered illustrative and not limiting as to the types of resins or dry chemicals used. 
     The packed resin or dry chemical bed  20  is disposed between a first screen  30  and a second screen  40  the design of which will be further described hereinbelow. The packed resin or dry chemical bed  20  includes a first cylindrical layer of a second resin or dry chemical material and comprises approximately 10% of the volume of the packed resin or dry chemical bed  20 . The second resin or dry chemical material is of a type which preconditions halogen species in the effluent gases produced in a semiconductor fabrication tool (not shown). The second resin or dry chemical is an acid neutralizing composition consisting of metal hydroxides on an extruded, pelletized clay substrate. The second resin or dry chemical material is available from C&amp;M Inc., #308 Sungwoo Plaza, 1047-6 Hogye-Dong, Dongan-Gu, Anyang City, Kyngki-Do, Korea under the tradename CM2. A table of representative reactions in the first layer  22  is shown in FIG.  3 . 
     A first cylindrical layer  24  of a first resin or dry chemical material comprises approximately 80% of the volume of the packed resin or dry chemical bed  20  and is disposed between the first layer  22  of the second resin or dry chemical material and a second cylindrical layer  26  of the second resin or dry chemical material. The first resin or dry chemical material is of a type which reacts with halogenated species and perfluoro compounds as shown in the table in FIG.  2 . The first resin or dry chemical material is a composition consisting of nitrate compounds on a steam-activated extruded carbon substrate. The first resin or dry chemical material is available from C&amp;M Inc. under the tradename CM1. The second layer  26  of the second resin or dry chemical material is operable to react with, and has a high capacity for, Cl −  species as the effluent gases exit the packed resin or dry chemical bed  20 . 
     A preferred embodiment of an end of life monitor and predictor system includes a plurality of thermocouples embedded in the first layer  24  of the first resin or dry chemical. Each of the plurality of thermocouples is embedded in the first layer  24  at an edge portion thereof (not shown). The thermocouples are preferably of pt 100 ohm type. Preferably, a first thermocouple  50  is embedded in the first layer  24  of the first resin or dry chemical at a first position approximately {fraction (4/10)} of the distance from the bottom screen  30  and the top screen  40 . A second thermocouple  52  is preferably embedded in the first layer  24  of the first resin or dry chemical at a second position {fraction (6/10)} of the distance from the bottom screen  30  to the top screen  40 . A third thermocouple  54  is preferably embedded in the first layer  24  of the first resin or dry chemical at a third position {fraction (8/10)} of the distance from the bottom screen  30  to the top screen  40 . In this configuratioln the distance between the first position and the second position is the same as the distance between the second position and the third position. Furthermore, the distance between the third position and an interface between the first layer  24  of the first resin or dry chemical and the second layer  26  of the second resin or dry chemical is half the distance between the second position and the third position. 
     Thermocouples  50 ,  52  and  54  are operably coupled to a processor (not shown) operable to monitor the motion of an exothermic wavefront which moves through the packed resin or dry chemical bed  20  as effluent gases flow through the canister  10 . The wavefront is kept as uniform as possible by urging an upward laminar flow of the gases through the system. A plurality of well type connectors (not shown) are formed in the canister  10  through which cables (not shown) connect the thermocouples  50 ,  52 , and  54  to the processor. Those skilled in the art will appreciate that the processor may include a microprocessor, a programmable logic controller, a discreet circuit or any other device or circuit for providing an output representative of the thermocouple output. The processor is operable to monitor the motion of the exothermic wavefront by sampling the thermocouples  50 ,  52 , and  54  and recording the temperature at each of the first, second and third positions over time. By way of example and not limitation, and making reference to the table shown in FIG. 4, a method of predicting the end of life of the first layer  24  of the first resin or dry chemical will now be described. The actual temperatures are simplified for the purposes of the example. 
     In FIG. 4, at a beginning time T 1 , thermocouple  50  indicates that the temperature at the first position is 50° C., thermocouple  52  indicates that the temperature at the second position is 25° C. and thermocouple  54  indicates that the temperature at the third position is 20° C. At a time T 2 , thermocouple  50  indicates that the temperature at the first position is 25° C., thermocouple  52  indicates that the temperature at the second position is 50° C. and thermocouple  54  indicates that the temperature at the third position is 25° C. At a time T 3 , thermocouple  50  indicates that the temperature at the first position is 20° C., thermocouple  52  indicates that the temperature at the second position is 25° C. and thermocouple  54  indicates that the temperature at the third position is 50° C. One skilled in the art will appreciate that the elevated temperatures (50° C.) indicate the positioning of the exothermic wavefront at the respective first, second or third positions within the first layer  24  of the first resin or dry chemical. The processor is operable to compute a time ΔT 21 =T 2 −T 1  and a time ΔT 32 =T 3 −T 2 . It is expected that ΔT 21  will be approximately equal to ΔT 32 . The end of life of the first layer  24  of the first resin or dry chemical is then computed as (ΔT 21 )/2 since the exothermic wavefront can be expected to travel through the remaining portion of the first layer  24  of the first resin or dry chemical in half the time. 
     In order to urge a uniform movement of the exothermic wavefront through the packed resin or dry chemical bed  20 , laminar flow of the effluent gases from the semiconductor fabrication tool through the packed resin or dry chemical bed  20  is provided. Laminar flow is established through the packed resin or dry chemical bed  20  by providing a dispersion nozzle  60  in communication with a canister inlet port  70  which disperses the effluent gases in a canister bottom plenum  12 , first and second screens  30  and  40  which further disperse and distribute the effluent gases within the canister  10  and a dome  80  of semicircular cross section which encloses a canister top plenum  14 . 
     With reference to FIG. 5, the dispersion nozzle  60  is shown including an elongated cylindrical portion  62  extending from the canister inlet port  70  and terminating at a downwardly angled portion  64 . A plurality of apertures  66  are spacedly formed along the elongated portion  62  on opposite sides of the elongated portion  62  (opposite side apertures not shown) and disposed below an equatorial plane of the elongated portion  62  to direct incoming effluent gases to the bottom of the bottom plenum  12  (FIG.  1 ). 
     As shown in FIG. 6, a pair of apertures  68  arc shown formed in the downwardly angled portion  64 . By virtue of the orientation of the downwardly angled portion  64 , effluent gases flowing through the apertures  68  are directed to the bottom of the bottom plenum  12 . 
     The combined areas of the apertures  66  and apertures  68  is greater than the area of a cross section of the elongated portion  62  to reduce the chance that back pressure will develop forcing the effluent gases back into the semiconductor fabrication tool. 
     With reference to FIG. 7, the dome  80  includes a semicircular cross sectional profile. The dome  80  further includes an outlet port  90  to which is generally attached a fan or vacuum source (not shown) to draw the effluent gases through the canister  10  for processing. The design of the dome  80  reduces “dead spaces” in the packed resin or dry chemical bed  20  in an area proximate the second layer  26  and promotes laminar flow of the effluent gases through the canister  10 . 
     As seen in FIG. 1, first and second screens  30  and  40  respectively are provided for enclosing the packed resin or dry chemical bed  20  within the canister  10 . As shown in FIG. 8, the first screen  30  includes a circular member having a preferred thickness of 10 mm and a plurality of apertures  32  formed therethrough. The apertures  32  are sized and configured to retain the packed resign bed  20  above the first screen  30  and are preferably less than 3 mm in diameter, the second resin or dry chemical material having a diameter greater than 3 mm. As shown in FIG. 1, the first screen  30  provides support for the first layer  22  of second resin or dry chemical material and further provides a boundary between the packed resin or dry chemical layer  20  and the bottom plenum  12 . As will be appreciated by those skilled in the art, the apertures  32  further provide for the dispersal of the effluent gases dispersed by the dispersal nozzle  60  and as such provide for laminar flow through the packed resin or dry chemical bed  20 . 
     The second screen  40  is of identical size and configuration as the first screen  30  and is disposed at a top of the second layer  26  of the second resin or dry chemical. The second screen  40  further provides a bottom of the top plenum  14 . The second screen additionally provides for laminar flow through the packed resin or dry chemical bed  20 . 
     As shown in FIG. 1, the canister  10  is comprised of three sections. A first section  16  provides an enclosure for the bottom plenum  12 . The first section  16  is preferably joined to a second section  18  which provides an enclosure for the packed resin or dry chemical bed  20  at a first flange  32 . To the second section  18  is joined the dome  80  at a second flange  42 . As shown the first and second screens  30  and  40  are disposed at the first and second flanges  32  and  42  respectively. 
     A common problem encountered in packed resin or dry chemical bed scrubbers involves the clogging of the device by particles created in the reaction of the effluent gases with the resin or dry chemical material. A preferred embodiment provides for a sight glass  100  as shown in FIGS. 1,  9  and  10 . The sight glass  100  is positioned at a bottom portion of the canister  10  and oriented to provide a view of the dispersion nozzle  60 . A flange  102  formed on an outside portion of the canister  10  includes a claw clamp  104  for securing a removable glass member  106  from the flange  102 . 
     Visual inspection of the bottom plenum  12 , dispersion nozzle  60  and bottom screen  30  is made possible by the positioning of the sight glass  100 . In the case where a buildup of particles is observed in any of the bottom plenum  12 , the dispersion nozzle  60  or the bottom screen  30 , the glass member  106  may be removed in-situ and these components accessed as with a vacuum cleaning device  120  (FIG. 11) for removal of the accumulated particles. Removal of particles from the dispersion nozzle  60  prevents the build-up of back pressure in the semiconductor fabrication tool and prevents particles from reaching the fabrication tool. As previously described, the bottom screen  30  functions to ensure laminar flow through the packed resin or dry chemical bed  20  and thus the removal of particles therefrom is important in maintaining such laminar flow. 
     In use, the effluent gases of the semiconductor fabrication tool enter the canister  10  at the inlet  70 . A pressure differential between the top plenum  14  and the bottom plenum  12  is created by an exhaust or vacuum source connected to the outlet  90 . The effluent gases are dispersed by the dispersion nozzle  60  and directed to the bottom of the bottom plenum  12 . The effluent gases are next drawn through the bottom screen  30  and through the packed resin or dry chemical bed  20 . Laminar flow through the packed resin or dry chemical bed  20  provides for a uniform exothermic wavefront which travels through the packed resin or dry chemical bed  20  as the effluent gases react with the constituents of the packed resin or dry chemical bed  20 . The thermocouples  50 ,  52  and  54  coupled to the processor detect and monitor the movement of the exothermic wavefront and the processor is operable to predict the end of life of the packed resin or dry chemical bed  20 . 
     In a preferred embodiment, the canister  10  is formed from stainless steel and is 1370 mm high and has an internal diameter of 444 mm. The dome  80  has a radius of 222 mm and is joined to a bottom of the canister at a position corresponding to the position of the second screen  40 . The packed resin or dry chemical bed  20  has a depth of 876 mm and the bottom plenum  12  has a depth of 151.5 mm. The first and second screens  30  and  40  have a diameter of 440 mm. As shown in FIG. 1, the canister  10  further includes a plurality of casters  110  disposed at a bottom surface thereof for providing mobility to the canister  10 . 
     The dispersion nozzle  60  is preferably 260 mm long and 38.1 mm in diameter, the angled portion  64  being angled in a downward direction and extending from an end of the dispersion nozzle and terminating at a position 38 mm from the end of the dispersion nozzle. 
     While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of an embodiment of the disclosed invention should not be limited by any of the above described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.