Patent Publication Number: US-2006013745-A1

Title: Enhanced PFC waste-gas treating system

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention is related to an enhanced PFC waste-gas treating system, and especially to a waste-gas treating system designed for treating the waste gases created in general semiconductor processing in production; the waste-gas treating system mainly is provided at one side of a waste-gas treating equipment, and is used to secondarily treat the residual gases containing PFC (per-fluorine compound), so that the gases containing PFC can be totally decomposed, and thereby the gases will not make damage to the environment or human bodies during exhausting the gases to the atmosphere.  
      2. Description of the Prior Art  
      Whereas the industry of semiconductor (including high-tech electric elements such as microprocessors, memories, integrated circuits . . . etc.) have really been the center of development of the modern industry; however, the industry of semiconductor needs to use large amount of water, electricity and dangerous as well as harmful chemical materials.  
      Particularly in the process of production, large amount of dangerous and harmful chemical agents such as methyl triethoxy silicane (TEOS), hydrofluoride acid (HF), nitrogen oxide (NO X ), hydrogen phosphide (PH 3 ), hydrogen arsenide (AsH 3 ) and (per-fluorine compound) PFC etc. Wherein if the toxic substance (per-fluorine compound) PFC such as nitrogen trifluoride (NF 3 ), sulfur hexafluoride (SF 6 ), carbon tetrafluoride (CF 4 ), C 3 F 8  and C 2 F 6  etc. is not well treated and is exhausted to the atmosphere, it not only pollutes the environment, but also makes enlargement of the hothouse effect.  
      Thereby in the process of production, a waste-gas treating equipment  1  must be used to treat toxic gases created after production. Referring to  FIG. 1 , conventional waste-gas treating equipments are divided into two kinds: the single type treating equipments and the composite treating equipments. The single type treating equipments include the thermoelectric type, the water cleansing type, the plasma type, the adsorption type and the combustion type; the composite treating equipments mainly are combinations each of more than two single type treating equipments, such as a composite treating equipment composed of a thermoelectric type plus a water cleansing type, or a thermoelectric type plus a water cleansing type and an adsorption type etc.  
      However, no matter a treating equipment belongs to the single type treating equipments (water cleansing type) or the composite treating equipments (a thermoelectric type plus a water cleansing type), it is unable to have the per-fluorine compound (PFC) contained in waste gases created during the process of production been effectively treated for removing, and a singular catalyst type equipment is unable to effectively treat other waste gases created during the process of semiconductor production, it can not be widely used to treat waste gases of semiconductor industry.  
      Thereby, the waste-gas treating system of the present invention can be connected with a composite treating equipment (a thermoelectric type plus a water cleansing type), the composite treating equipment can have the waste gases created during the process of semiconductor production other than PFC, and then the waste-gas treating system of the present invention is used to effectively treat the per-fluorine compound (PFC) contained in waste gases that the composite treating equipment (a thermoelectric type plus a water cleansing type) is unable to effectively remove in the former stage.  
      Therefore, the waste-gas treating system of the present invention can treat per-fluorine compound (PFC) that the composite treating equipment (a thermoelectric type plus a water cleansing type) is unable to effectively remove, and can be widely used to treat waste gases of the semiconductor industry.  
     SUMMARY OF THE INVENTION  
      In view of the above statement, the inventor of the present invention developed successfully an enhanced PFC waste-gas treating system based on his professional experience of years in studying, designing and manufacturing as well as after hard study and development.  
      Thereby, the enhanced PFC waste-gas treating system of the present invention mainly is provided at one side of a waste-gas treating equipment, and is used to secondarily treat the residual gases containing PFC (per-fluorine compound) after treating by the waste-gas treating equipment, so that the gases containing PFC can be totally decomposed, and thereby the gases will not make environmental pollution during exhausting the gases outside, and can effectively prevent enlargement of the hothouse effect. The system contains therein mainly a condensing tube, a catalyst treating unit, a water treating unit and water collecting tanks, the catalyst treating unit decomposes toxic gases such as per-fluorine compound (PFC) etc. to form non-toxic gases, and the byproduct from decomposing is subjected to water treating by means of the water treating unit, thus a function of lowering temperature can be acquired, then the gases are exhausted to the atmosphere to lower the damage of pollution of the semiconductor industry to the environment.  
      The object of the present invention is: by condensing of the condensing tube in a front section to deal with the water vapor created by the composite treating equipment (a thermoelectric type plus a water cleansing type), the resulted material enters the catalyst treating unit having therein gas of per-fluorine compound (PFC) to keep it dry, and the catalyst treating unit dissociates the gases containing the per-fluorine compound (PFC), and the byproduct created by dissociation when entering the water treating unit is converted into gases not harmful to human bodies. And a function of lowering temperature can be acquired; then the gases are exhausted to the atmosphere to lower the damage of pollution of the semiconductor industry to the environment.  
      The present invention will be apparent in its content and effects to be achieved after reading the detailed description of the preferred embodiment thereof in reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic perspective view of a conventional waste-gas treating equipment;  
       FIG. 2  is a schematic perspective view showing application of the present invention;  
       FIG. 3  is a perspective view of the present invention;  
       FIG. 4  is a schematic sectional view of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      The enhanced PFC waste-gas treating system of the present invention mainly is provided at one side of a waste-gas treating equipment  1 , as shown in  FIGS. 2 and 3 , it comprises a machine main body  10 , the machine main body  10  is provided exteriorly thereof with a gas inlet  11  and a gas exhausting tube  12 ; the gas inlet  11  is connected with the waste-gas treating equipment  1  to guide the gases exhausted from the latter, the gas exhausting tube  12  is connected with a gas drawing pump unit  13  to exhaust the gases in the machine main body  10 .  
      Referring simultaneously to  FIG. 4 , the machine main body  10  is provided therein further with two water collecting tanks  14 , a front-section condensing tube  15 , a catalyst treating unit  16 , a water treating unit  17  and a rear-section condensing tube  18 ; wherein a first water collecting tank  141  is provided with the front-section condensing tube  15  and the catalyst treating unit  16 , a second water collecting tank  142  is provided with the water treating unit  17  and the rear-section condensing tube  18 . The catalyst treating unit  16  and the water treating unit  17  are connected with each other via a pipeline  19 , the front-section condensing tube  15  is connected with the gas inlet  11  exteriorly of the machine main body  10 , while the rear-section condensing tube  18  is connected with the gas exhausting tube  12  also exteriorly of the machine main body  10 .  
      The catalyst treating unit  16  is provided therein with a catalyst tube  161 , the water treating unit  17  is provided-therein with a water spraying pipe  171  and an adsorption element  172 , and the first water collecting tank  141  and the second water collecting tank  142  are connected with the waste-gas treating equipment  1  respectively through guiding tubes  20 .  
      Thereby, when the gases containing PFC (per-fluorine compound) such as NF 3 , SF 6 , and C 2 F 6  etc. enters the machine main body  10  through the gas inlet  11  after treatment of the waste-gas treating equipment  1 , the front-section condensing tube  15  converts the water vapor contained in the gas of per-fluorine compound (PFC) into the state of water solution to stay in the first water collecting tank  141 , thereby the gases containing the per-fluorine compound (PFC) can keep dry and enter the catalyst treating unit  16 , the gases containing the per-fluorine compound (PFC) (such as NF 3 , SF 6 , and C 2 F 6  etc.) is dissociated by the catalyst tube  161  in the catalyst treating unit  16 , the chemical equation of this is as follows: 
 
NF 3 →HF+F 2 +NO X  
 
SF 6 →HF+F 2 +SO X  
 
C 2 F 6 →HF+F 2 +CO 2  
 
      Then the gases after dissociation are led by the pipeline  19  into the water treating unit  17 , by virtue that the water treating unit  17  is provided therein with the water spraying pipe  171  and the adsorption element  172  (in the embodiment of the present invention, the water treating unit  17  is divided into an upper and a lower layer, each of these layers is provided with the water spraying pipe  171  and the adsorption element  172 ), so that an operation of water sprinkling can be performed by means of the water spraying pipe  171  to do water treating on the gas byproducts such as HF, F 2 , NO X , SO X , SiF 4  etc., and to make their temperature lower, the chemical equation of this is as follows: 
 
HF(g)→HF(ag) 
 
F 2 +H 2 O→HF(ag)+O 2  
 
      The gases obtained after dissociation by the catalyst treating unit  16 , such as the gases HF, F 2 , SiF 4  etc., are again converted into non-toxic gases such as HF (ag),  0   2  etc. by the water treating unit  17 , then the non-toxic gases and water are led into the second water collecting tank  142 , lastly, water vapor is dealt with by the rear-section condensing tube  18 , and the gas drawing pump unit  13  is used to discharge the non-toxic gases to the atmosphere via the gas exhausting tube  12 , hence the gases exhausted will not be harmful to the environment and human bodies.  
      As stated above, by virtue that the water treating unit  17  is provided therein with the adsorption element  172 , and the adsorption element  172  is made of ceramic material (i.e., a Raschig ring), so that the contact area of water with gases such as HF, F 2 , SiF 4  etc. obtained after dissociation and detaining time of them can be increased by the aid of the adsorption element  172 , so that the gases such as HF, F 2 , SiF 4  etc. obtained after dissociation can be completely decomposed to form non-toxic gases in the water treating unit  17 .  
      And more, referring to FIGS.  2  to  4 , wherein the gas inlet  11  and the gas exhausting tube  12  are connected therebetween with a pneumatic valve  30  which is shut in normal use, while the gas inlet  11  and the front-section condensing tube  15 , the gas exhausting tube  12  and the rear-section condensing tube  18  are both connected therebetween with a manually valve  40  which is in an opened stated in normal use. Thereby, when the interior of the machine main body  10  is out of order or when it is in maintenance or changing the catalyst tube  161 , the passageways between the gas inlet  11  and the front-section condensing tube  15  as well as between the gas exhausting tube  12  and the rear-section condensing tube  18  can be cut short by means of the manually valve  40 , the gases are forced to be led to the gas exhausting tube  12  via the pneumatic valve  30  for exhausting to avoid damage of the interior of the machine main body  10 .  
      The gas inlet  11  is provided on the outer surface thereof with a pressure detector  50  to detect the inner pressure of the gas inlet  11 ; and the catalyst treating unit  16  is provided on the outer surface thereof with a temperature sensor  60  to detect the inner temperature of the catalyst treating unit  16 , thereby to avoid damage of the catalyst treating unit  16  because of overly high temperature induced in the catalyst treating unit  16 . And the rear-section condensing tube  18  is provided on the outer surface thereof with a gas detector  70  to detect whether there are residual gases containing per-fluorine compound (PFC), in order to maintain normal operation of the whole waste-gas treating system.  
      Moreover, a control unit  80  is provided on the outer wall of the machine main body  10 , the control unit  80  is further provided with a plurality of control buttons  81  to control components in the machine main body  10 , thereby the entire waste-gas treating system can be more convenient in use.  
      The names of the members are only for illustrating a preferred embodiment of the present invention, and not for giving any limitation to the scope of the present invention. It will be apparent to those skilled in this art that various equivalent modifications or changes made to the present invention without departing from the spirit thereof shall fall within the scope of the appended claims.