Abstract:
The invention relates to a method of purifying a fluoride in a semiconductor process waste gas. The method comprises the steps of importing a mist gaseous water at a high temperature produced by heating water in a reaction chamber of a semiconductor waste gas treating tank; and dissolving the fluoride into a hydrogen fluoride by using the mist gaseous water, wherein a dissolving temperature of the mist gaseous water contacting with the fluoride is 370˜1300° C. This invention provides a device of purifying a fluoride in a semiconductor process waste gas. The conventional problems saying that the steps and structure of the device of purifying the fluoride in the semiconductor process waste gas are too complex and a purifying efficiency is hard to be increased.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a purifying technique of a semiconductor process waste gas, especially to a method and a device of purifying a fluoride in a semiconductor process waste gas. 
         [0003]    2. Description of Related Art 
         [0004]    In order to mitigate a serious effect of a greenhouse effect on the global warming, the World Semiconductor Industry Association decides to list some special gases, such as, SF6, CF4, C2F6, C3F8, CHF3, NF3, F2 named as perfluorinated compounds, as reduction subjects of harmful gases rendering the greenhouse effect. 
         [0005]    Because the waste gases emitted from the semiconductor process including NF 3 , F 2  named as perfluorinated compounds will cause environment pollution after the harmful fluoride gases are emitted to the air, there are provided devices of processing semiconductor process waste gases. In a pre-processing reaction chamber for capturing the fluoride, generally by using a high temperature flame or a hot pin to be directly be guided or inserted into the pre-processing reaction chamber, the harmful fluoride gas is dissolved into a non-harmful fluoride ion so as to purify the waste gas. 
         [0006]    In the process of dissolving the fluoride gas into non-harmful fluoride ions by using the high temperature flame or the hot pin, a pre-washing process step is needed in the pre-processing reaction chamber of the waste gas treating tank to supply sufficient hydrogen ions so that the fluoride can react with the hydrogen ion in the water in a high temperature environment. However, the pre-washing process step is very time-consuming and proliferator produced in the water after the water molecular contacts with the fluoride will adhere to an inner wall of the reaction chamber of the waste gas treating tank. A water wall of dirt preventing or an additional cleaning step is needed and arranged for the inner wall of the reaction chamber, a purifying efficiency of dissolving the fluoride gas into non-harmful fluoride ions is decreased and a cost of the waste gas treating device and the purifying step increases. It is necessary to solve the above problems. 
       SUMMARY OF THE INVENTION 
       [0007]    It is an objective of the present invention to solve a problem saying that the conventional purifying process of the fluoride by using the high temperature flame or the hot pin is too complex in process step and in structure in the process of capturing the fluoride in the pre-processing reaction chamber of the semiconductor waste gas treating tank. In more details, in the present invention a fluorine atom will be very active in a specific high temperature environment, the water molecular will exhibit properties of a mist gaseous water in order to capturing the fluoride by using the mist gaseous water molecules at a high temperature, the fluoride is dissolved into a fluoride hydrogen (HF) and the purifying efficiency of the gas is increased. 
         [0008]    In order to solve the problems, it is another objective of the present invention to provide a method of purifying a fluoride in a semiconductor process waste gas comprising the steps of: 
         [0009]    importing a mist gaseous water at a high temperature produced by heating water in a reaction chamber of a semiconductor waste gas treating tank; and 
         [0010]    dissolving the fluoride into a hydrogen fluoride by using the mist gaseous water, wherein a dissolving temperature of the mist gaseous water contacting with the fluoride is 370˜1300° C. 
         [0011]    According to the present invention, the mist gaseous water is preferably imported into the reaction chamber by spraying. 
         [0012]    According to the present invention, the capturing ring preferably has a plurality of tongue strips formed on a circumferential wall of the capturing ring extending at a direction of the axis line. 
         [0013]    According to the above method, it is another objective of the present invention to provide a device of purifying a fluoride in a semiconductor process waste gas, comprising: 
         [0014]    a reaction chamber formed in a waste gas treating tank of semiconductor having at least one guide pipe of the semiconductor process waste gas for guiding and entering the semiconductor process waste gas comprising the fluoride into the reaction chamber; and 
         [0015]    a heat pipe disposed in the waste gas treating tank and inserted into the reaction chamber, the heat pipe having an outside end formed at an outside of the waste gas treating tank and an inner end formed in the reaction chamber, a water injection pipe being disposed at the outside end, a plurality of spit-outs being disposed and formed at the inner end and passing through and arranged on a pipe wall of the heat pipe, wherein a heating rod is disposed in and passes through the heat pipe, a passage is formed between the heating rod and the heat pipe, the passage is fluidly connected to the water injection pipe and is fluidly connected to the reaction chamber via the plurality of spit-outs, water is guided and enters into the passage by the water injection pipe, the water in the passage contacts with the heating rod to produce a mist gaseous water at a high temperature, the mist gaseous water is guided and enters into the reaction chamber via the plurality of spit-outs to dissolve the fluoride to be reacted into a hydrogen fluoride, and a dissolving temperature of the mist gaseous water contacting with the fluoride is 370˜1300° C. 
         [0016]    According to the present invention, the mist gaseous water is preferably guided and enters into the reaction chamber via the plurality of spit-outs by spraying. 
         [0017]    According to the present invention, the plurality of spit-outs preferably pass through and extend through, and the plurality of spit-outs are disposed around a surrounding pipe wall of the heat pipe located at the inner end. 
         [0018]    According to the present invention, a top cover is preferably disposed at a top side of the semiconductor waste gas treating tank, and the guide pipe and the heat pipe of the semiconductor waste gas are spaced apart from each other and disposed at the top cover. 
         [0019]    According to the present invention, the heat pipe, the passage and the heating rod are preferably arranged in a concentric circle way of a straight line. 
         [0020]    According to the present invention, a ring heater used as a tank wall of the waste gas treating tank is preferably disposed at a periphery of the reaction chamber, and the dissolving temperature reaches when the ring heater is heating. 
         [0021]    According to the present invention, a plurality of reaction tanks are preferably formed in the reaction chamber by using a plurality of separator plates to separate, at least one holes fluidly connected to the plurality of reaction tanks are respectively formed on the plurality of separator plates, the plurality of reaction tanks are fluidly connected each other via the holes to form an air duct channel, and the air duct channel is used for guiding the waste gas and the mist gaseous water to move through the reaction chamber. 
         [0022]    According to the present invention, the holes respectively formed on the plurality of separator plates are preferably correspondent to each other located at a first to fourth quadrants in a X-/Y-coordinate plane in a staggered way so that the air duct channel is in a spiral form. 
         [0023]    According to the present invention, partition walls are preferably disposed between the plurality of separator plates. 
         [0024]    In accordance to the above method and the device, the technical effects of the present invention are as follows: In a process of capturing the fluoride in the pre-processing reaction chamber of the semiconductor waste gas treating tank, it is not necessary to use the conventional high temperature flame or the hot pin used together with a water supply step of fluoride of the pre-washing process, and the complex structure of the device is simplified. The purifying efficiency of the harmful fluoride by using capturing and dissolution of the high temperature mist gaseous water is increased. The purifying efficiency is higher than that of the conventional heating catalytic method by using the high temperature flame or the hot pin. 
         [0025]    Other objectives, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  is a explanative schematic diagram of a purifying method of the present invention. 
           [0027]      FIG. 2  is a three-dimensional explosive diagram showing a heat pipe of the present invention. 
           [0028]      FIG. 3  is a three-dimensional explosive diagram showing the heat pipe of  FIG. 2  according to the invention. 
           [0029]      FIG. 4  is a cross-section view showing an arrangement of the heat pipe in the semiconductor waste gas treating tank of  FIG. 2  of the present invention. 
           [0030]      FIG. 5  is a cross-section view showing a separator plate in the purifying device of the present invention. 
           [0031]      FIG. 5 a    is a cross-section view taken along A-A line of  FIG. 5  of the present invention. 
           [0032]      FIG. 5 b    is a cross-section view taken along B-B line of  FIG. 5  of the present invention. 
           [0033]      FIG. 5 c    is a cross-section view taken along C-C line of  FIG. 5  of the present invention. 
           [0034]      FIG. 5 d    is a cross-section view taken along D-D line of  FIG. 5  of the present invention. 
           [0035]      FIG. 6  is a cross-section view showing a separator plate arranged in the semiconductor waste gas treating tank of  FIG. 5  of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0036]    The scope and contents of the present invention are not limited to a scope of the following examples. 
         [0037]    Please refer to  FIG. 1  which discloses a schematic diagram of a method of purifying a fluoride in a semiconductor process waste gas of a preferred embodiment of the present invention. In the semiconductor process device, there are provided with a waste gas treating tank  2  in which a pre-processing reaction chamber  20  is formed. The waste gas including perfluorinated compounds (PFC) produced in the semiconductor process is guided into the pre-processing reaction chamber  20  in order to do pre-processing dissolution of the harmful perfluorinated compounds (PFC). 
         [0038]    In the present invention, a high temperature mist gaseous water  30  is guided into the pre-processing reaction chamber  20 . The so-called “guided” means that the gaseous water is sprayed to obtain a better effect. The high temperature mist gaseous water  30  is produced by heating room temperature water into steam. 
         [0039]    The water is heated at a temperature of 100° C. to produce steam. When the water continues to be heated to a temperature of 370° C. or above, mist gaseous water is generated. When water continues to be heated to a temperature of 950° C. or above, the hydrogen of the water molecular will be easily decomposed into gaseous hydrogen ion (H + ). Thus, the temperature of the water guided into the pre-processing reaction chamber  20  should be a high temperature from 370° C. to 1300° C. The requirement condition for exhibiting mist gaseous water is a temperature of 370° C. 
         [0040]    Because fluorine (F) is very reactive at a high temperature of 850° C., when a temperature of the pre-processing reaction chamber  20  reaches to 370˜1300° C., the perfluorinated compounds (PFC), such as NF3, F2, etc. will be fast dissolved into a fluoride ion (F − ) by the mist gaseous water  30  and the fluoride ion (F − ) will react with the gaseous hydrogen ion (H + ) generated by dissolving the mist gaseous water  30  to combine and to produce an aqueous hydrogen fluoride (HF). 
         [0041]    A following reaction equation I discloses a reaction equation when the fluoride is F 2 . 
         [0000]    
       
                 
         
             
             
         
       
     
         [0042]    A following reaction equation II discloses a reaction equation when the fluoride is 
         [0000]    
       
                 
         
             
             
         
       
     
       NF 3 . 
       [0043]    In one preferred embodiment, because fluorine (F) is very reactive at a high temperature of 850° C., when the mist gaseous water  30  in the pre-processing reaction chamber  20  is heated to a dissolving temperature of to 850˜1300° C., a purifying effect of the fluoride ion (F − ) in the dissolving perfluorinated compounds (PFC) is greatly increased and the fluoride ion (F − ) will easily react with the gaseous hydrogen ion (H + ) generated by dissolving the mist gaseous water  30  to combine and to produce an aqueous hydrogen fluoride (HF). The aqueous hydrogen fluoride (HF) is scrubbed and captured by the washing step of the after-processing waste gas treating tank  2  to form a non-harmful gas to be emitted to the outside (the washing step of the after-processing waste gas treating tank  2  is not the main point or the improvement of this invention, it will not described in more details). 
         [0044]    In order to concretely implement the method please refer to  FIGS. 2 to 4  which demonstrate a second preferred embodiment of the purifying device implemented in the invention. The  FIG. 2  discloses a structural diagram of a heat pipe  40 . The  FIG. 3  discloses a three-dimensional explosive diagram of the heat pipe  40 . The  FIG. 4  discloses an arrangement configuration of the heat pipe  40  disposed at the pre-processing reaction chamber  20  of the semiconductor waste gas treating tank  2 . 
         [0045]    Two guide pipes  21  of the semiconductor waste gas  10  are disposed at the waste gas treating tank  2 . The guide pipes  21  are fluidly connected to the pre-processing reaction chamber  20 . The guide pipes  21  are used for guiding the semiconductor process waste gas  10  containing the perfluorinated compounds (PFC) into the reaction chamber  20 . A top cover  23  is disposed at the top of the waste gas treating tank  2 . The guide pipes  21  are disposed at the top cover  23 . A nitrogen pipe  22  is fluidly connected to the guide pipes  21 . Nitrogen gas is guided by the nitrogen pipe  22  to enter into the reaction chamber  20  via the guide pipe  21 . 
         [0046]    A heat pipe  40  inserted into the reaction chamber  20  is disposed in the waste gas treating tank  2 . In implementation, the heat pipe  40  is spaced away from the guide pipe  21  of the semiconductor process waste gas  10  and disposed at the top cover  23 . At both ends of the heat pipe  40 , an outside end  41  located at an outside of the waste gas treating tank  2  and an inner end located at an inside of the reaction chamber  20  are formed. A water injection pipe  47  is fluidly connected to the outside end  41 . Room temperature water is guided by the water injection pipe  47  to enter into the heat pipe  40 . A plurality of spit-outs  44  spaced apart and passed through and disposed on the pipe wall  43  of the heat pipe  40  are formed on a periphery pipe wall  43  located at the inner end of the reaction chamber  20  on the heat pipe  40 . A heating rod  45  is inserted into and disposed at the heat pipe  40 . The heating rod  45  can be an electrothermal heating rod. The heating rod  45  is used for heating water injected from the water injection pipe  47  into the heat pipe  40  so as to reach a water temperature of 370˜1300° C. When the water is heated to reach a temperature of 370° C. or above to exhibit mist gaseous water which move out of the spit-outs  44  located on the pipe wall of the heat pipe  40  to form the mist gaseous water  30  to be guided into the reaction chamber  20 . 
         [0047]    In one embodiment, a passage  46  is formed between the heating rod  45  and the pipe wall  43  of the heat pipe  40 . The passage  46  is fluidly connected to the water injection pipe  47  and is fluidly connected to the reaction chamber  20  via the plurality of spit-outs  44  so as produce the mist gaseous water  30  at a high temperature by heating of the heating rod  45 . Thus, the mist gaseous water  30  enters the reaction chamber  20  via the spit-outs  44 . Because a cross-area of the spit-out  44  is smaller than that of the passage  46 , the mist gaseous water  30  enters the reaction chamber  20  by spraying. The heat pipe  40 , the passage  46  and the heating rod  45  are arranged in a concentric circle way of a straight line so that the mist gaseous water  30  enters the reaction chamber  20  from the different spit-outs  44  under the same pressure in order to uniformly spraying in the reaction chamber  20 . 
         [0048]    A ring heater  24  is disposed at the periphery of the reaction chamber  20 . The ring heater  24  is used as an inner tank wall of the waste gas treating tank  2  in one embodiment. The ring heater  24  is used for heating and maintaining the temperature in the reaction chamber  20  so as to the temperature of the waste gas  10  and the mist gaseous water  30  reach to a dissolving temperature and so as to increase a dissolving effect of the fluoride ion dissolved in the perfluorinated compounds (PFC) because the ring heater  24  is made by an electrothermal heating rod. Then, the fluoride ion (F − ) can be easily combined with the hydrogen ion (H + ) in the mist gaseous water  30  to produce an aqueous hydrogen fluoride (HF). The temperature of the guide pipe  21  inserted in the reaction chamber  20  is increased by the high temperature environment in the reaction chamber  20 . When the waste gas  10  moves through the guide pipe  21  and enters into the reaction chamber  20 , the temperature of the waste gas  10  is increase by contacting with the guide pipe  21  so that the temperature of the waste gas  10  can fast reach to the needed dissolving temperature to increase an purifying effect of the waste gas  10  during purifying duration. 
         [0049]    Please refer to  FIG. 4  which demonstrates that the waste gas  10  enters into the pre-processing reaction chamber  20  of the waste gas treating tank  2  via the guide pipe  21 . When the mist gaseous water  30  enters into the pre-processing reaction chamber  20  of the waste gas treating tank  2  via the spit-outs  44  located on the heat pipe  40 , the waste gas  10  and the mist gaseous water  30  which are heated up to the dissolving temperature by the heating rod  45  and the ring heater  24  chemically react with each other in the reaction chamber  20 . For example, the perfluorinated compounds (PFC), such as, NF 3 , F 2 , etc. are fast dissolved into the fluoride ion (F − ) by the mist gaseous water  30 , and the fluoride ion (F − ) combines with the gaseous hydrogen ion (H + ) dissolved in the mist gaseous water  30  to produce the aqueous hydrogen fluoride (HF). The waste gas  10  containing the hydrogen fluoride (HF) is sequentially moved from the pre-processing reaction chamber  20  in the waste gas treating tank  2  and pass through the first air washer  25  and the second air washer  26  located at the post-processing part in the waste gas treating tank  2 . The aqueous hydrogen fluoride (HF) is dissolved in the water during a scrubbing step via the first air washer  25  and the second air washer  26  so as to convert the waste gas  10  into non-harmful gas. The non-harmful gas is emitted to the outside atmosphere via the gas discharge port  27 . 
         [0050]    Please refer to  FIGS. 5 and 6  which demonstrate implementation details of a third embodiment of a purifying device of the present invention.  FIG. 5  discloses a cross-section view of the separator plate.  FIGS. 5 a  to 5 d    disclose cross-section views of the separator plate of  FIG. 5  at different locations.  FIG. 6  discloses a configuration view of the separator plate disposed at the pre-processing reaction chamber of waste gas treating tank. 
         [0051]    Please refer to  FIGS. 5 and 6 . In one embodiment a plurality of separator plates  50  are disposed in the reaction chamber  20 . The plurality of separator plates  50  are arranged and spaced apart in the reaction chamber  20  by locking means or soldering. A reaction tank  53  is formed between the plurality of separator plates  50 . The reaction tanks  53  are fluidly connected to each other via the holes  51  formed on the separator plates  50  so as to form an air duct channel  54 . The waste gas  10  and the mist gaseous water  30  are guided to move through the reaction chamber  20  by the air duct channel  54 . 
         [0052]    The plurality of separator plates  50  disclosed in  FIG. 5  comprise a first separator plate  50   a,  a second separator plate  50   b,  a third separator plate  50   c  and a fourth separator plate  50   d.  Form  FIGS. 5 a  to 5 d    it can be known that the holes  51  formed on the first separator plate  50   a,  the second separator plate  50   b,  the third separator plate  50   c  and the fourth separator plate  50   d  are correspondent to each other and located at a first to fourth quadrants in a X-/Y-coordinate plane in a staggered way. The holes  51  formed on the separator plates  50   a  to  50   d  can be in a single hole way or in a web-like hole layer. A partition wall  52  for partially separating the reaction tanks  53  is disposed between the separator plates  50 . Furthermore, the partition wall  52  is used for guiding and connecting the reaction tanks  53  via the holes  51  disposed on the neighboring separator plates  50  so as to construct and to form the tortuous air duct channel  54 . Thus, the waste gas  10  and the mist gaseous water  30  are guided to move through the reaction tanks  53  and to increase a staying duration of the waste gas  10  and the gaseous water  30  in the reaction tanks  53  in order to increase the converting efficiency of perfluorinated compounds (PFC) dissolved in the waste gas  10  converted into the hydrogen fluoride (HF) by the gaseous water  30 . 
         [0053]    Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that any other possible modifications and variations can be made without departing from the scope of the invention as hereinafter claimed.