Patent Publication Number: US-2023144685-A1

Title: Apparatus for processing substrate

Description:
This application claims the benefit of Korean Patent Application No. 10-2021-0154929, filed on Nov. 11, 2021, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Field 
     The present invention relates to a substrate processing apparatus. 
     2. Description of the Related Art 
     The semiconductor device manufacturing process may be continuously performed in a semiconductor manufacturing facility, and may be divided into a pre-process and a post-process. The semiconductor manufacturing facility may be installed in a space defined as a FAB to manufacture semiconductor devices. 
     The pre-process refers to a process of forming a circuit pattern on a wafer to complete a chip. These pre-processes may comprise a deposition process for forming a thin film on a substrate, a photo lithography process for transferring a photo resist onto a thin film using a photo mask, an etching process for selectively removing unnecessary parts using chemical substances or reactive gases in order to form a circuit pattern, an ashing process for removing the photoresist remaining after etching, an ion implantation process for implanting ions into the portion connected to a circuit pattern to have characteristics of an electronic device, a cleaning process for removing contamination sources from the substrate, and the like. 
     The post-process refers to the process of evaluating the performance of the finished product through the pre-process. The post-process may comprise a board inspection process that selects good and bad products by inspecting whether each chip on the board operates, the package process that cuts and separates each chip through dicing, die bonding, wire bonding, molding, and marking to shape the product, a final inspection process that finally checks the product characteristics and reliability through electrical characteristic inspection, and burn-in inspection, and the like. 
     When performing a substrate processing process, it is necessary to fix the substrate on the substrate support unit. As the structure of a substrate processing apparatus becomes simpler in recent years, a substrate support unit other than an electrostatic chuck may be used, and in this case, a method for fixing the substrate may be required. 
     SUMMARY 
     An object of the present invention is to provide a substrate processing apparatus including a substrate support unit connected to a vacuum pump to fix a substrate. 
     An object of the present invention is to provide a substrate processing apparatus including a substrate support unit that improves efficiency of heat transfer to a substrate. 
     The objects of the present invention are not limited to the objects mentioned above, and other objects not mentioned will be clearly understood by those skilled in the art from the following description. 
     The substrate processing apparatus of the present invention for achieving the above object comprises a chamber including a processing space therein, a substrate support unit disposed in the processing space and for supporting a substrate, a first vacuum pump, a second vacuum pump connected to the processing space of the chamber, a first valve disposed between the first vacuum pump and the second vacuum pump, and a second valve disposed between the first vacuum pump and the substrate support unit, wherein the first vacuum pump reduces a pressure in a space between the substrate support unit and the substrate to fix the substrate to the substrate support unit in response to the second valve being turned on. 
     The substrate processing apparatus of the present invention for achieving the above object comprises a chamber including a processing space therein, a substrate support unit disposed in the processing space and for supporting a substrate, a first vacuum pump, a second vacuum pump connected to the first vacuum pump, a first valve connected between the second vacuum pump and the processing space of the chamber, and a second valve disposed between the second vacuum pump and the substrate support unit, wherein the second vacuum pump reduces a pressure in a space between the substrate support unit and the substrate to fix the substrate to the substrate support unit in response to the second valve being turned on. 
     The substrate processing apparatus of the present invention for achieving the above object comprises a chamber including a processing space therein, a substrate support unit disposed in the processing space and including an upper exposed hole and a flow path connected to the hole, a first vacuum pump connected to the processing space through a first valve, a second vacuum pump connected to the first vacuum pump through a second valve and connected to the processing space through a third valve, and a fourth valve connecting the flow path of the substrate support unit and the first vacuum pump, wherein the first vacuum pump reduces a pressure in the processing space in response to the first valve being turned on, wherein the second vacuum pump reduces a pressure in the processing space in response to the second valve and the third valve being turned on, wherein the first vacuum pump reduces a pressure of the flow path to fix the substrate to the substrate support unit in response to the substrate being mounted on the substrate support unit and the fourth valve being turned on, wherein the fourth valve is turned off after processing of the substrate is completed, wherein the substrate is carried out after the fourth valve is turned off. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings in which: 
         FIG.  1    is a diagram of a substrate processing apparatus according to some embodiments; 
         FIG.  2    is a stereoscopic view of the substrate support unit of  FIG.  1   ; 
         FIG.  3    is a cross-sectional view of the substrate support unit taken along line A-A of  FIG.  2   ; 
         FIGS.  4  and  5    are top views of a substrate support unit according to some embodiments; 
         FIG.  6    is a flowchart of a method of operating a substrate processing apparatus according to some embodiments; 
         FIGS.  7  to  9    are views for describing a method of operating a substrate processing apparatus according to some embodiments; 
         FIG.  10    is a flowchart illustrating a method of operating a substrate processing apparatus according to another exemplary embodiment; 
         FIG.  11    is a diagram of a substrate processing apparatus according to some embodiments; and 
         FIG.  12    is a diagram of a substrate processing apparatus according to some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Advantages and features of the present disclosure and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present disclosure is not limited to the embodiments described below, but may be implemented in various different forms, and these embodiments are provided only for making the description of the present disclosure complete and fully informing those skilled in the art to which the present disclosure pertains on the scope of the present disclosure, and the present disclosure is only defined by the scope of the claims. Like reference numerals refer to like elements throughout. 
     Referring to an element or layer “on” another element or layer includes not only directly on the other element or layer, but also with intervening other layers or elements. On the other hand, referring to an element “directly on” indicates that no intervening element or layer is interposed. 
     Spatially relative terms “below,” “beneath,” “lower,” “above,” and “upper” can be used to easily describe a correlation between an element or components and other elements or components. The spatially relative terms should be understood as terms including different orientations of the device during use or operation in addition to the orientation shown in the drawings. For example, when an element shown in the figures is turned over, an element described as “below” or “beneath” another element may be placed “above” the other element. Accordingly, the exemplary term “below” may include both directions below and above. The device may also be oriented in other orientations, and thus spatially relative terms may be interpreted according to orientation. 
     Although first, second, etc. are used to describe various elements, components, and/or sections, it should be understood that these elements, components, and/or sections are not limited by these terms. These terms are only used to distinguish one element, component, or section from another element, component, or section. Accordingly, the first element, the first component, or the first section mentioned below may be the second element, the second component, or the second section within the technical spirit of the present disclosure. 
     The terminology used herein is for the purpose of describing the embodiments and is not intended to limit the present invention. In this specification, the singular also includes the plural unless otherwise specified in the phrase. As used herein, “comprises” refers to the presence or addition of one or more other components, steps, operations and/or elements mentioned is not excluded. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used with the meaning commonly understood by those of ordinary skill in the art, to which the present invention belongs. In addition, terms defined in a commonly used dictionary are not to be interpreted ideally or excessively unless clearly specifically defined. 
     Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings, and in the description with reference to the accompanying drawings, the same or corresponding components are given the same reference numbers, regardless of reference numerals in drawings, and an overlapped description therewith will be omitted. 
       FIG.  1    is a diagram of a substrate processing apparatus according to some embodiments. 
     Referring to  FIG.  1   , a substrate processing apparatus  1  may comprise an exhaust device  100 , a gas supply device  200 , an electrode module  300 , a controller  400 , and a chamber  500 . 
     The chamber  500  may provide a processing space  501  therein, in which the substrate W is processed. Here, the chamber  500  may have a circular cylindrical shape. The chamber  500  may include a metal material. For example, the chamber  500  may be made of aluminum. The opening  520  may be formed at one side of the chamber  500 . The opening  520  may correspond to an entrance, through which the substrate W can be carried in and out. Here, the opening  520  may be opened and closed by a door. 
     The transfer robot  530  may pass through the opening  520  to carry in or out the substrate W. For example, when the opening  520  is opened, the transfer robot  530  may pass through the opening  520  to place the substrate W on the substrate support unit  510  in the processing space  501 . After the process for the substrate W is finished, the transfer robot  530  may carry out the substrate W from the substrate support unit  510 . At this time, the transfer robot  530  may pass through the opening  520 . 
     The chamber  500  may include a substrate support unit  510  disposed in the processing space  501 . Here, the substrate support unit  510  may be referred to as a chuck. The substrate support unit  510  may support the substrate W and may fix the substrate W so that the substrate W does not move. Also, the substrate support unit  510  may include a heater for heating the substrate W. Here, the substrate support unit  510  may be located in the central portion of the chamber  500 . The substrate support unit  510  may be connected to the exhaust device  100 , but may not be connected to the gas supply device  200  and the electrode module  300 . However, embodiments of the present invention are not limited thereto. 
     The gas supply device  200  may include a first process gas supply unit  210 , a second process gas supply unit  220 , and a third process gas supply unit  230 . The first to third process gas supply units  210 ,  220 ,  230  may provide different gases to the electrode module  300  and the chamber  500 . For example, the first process gas supply unit  210  may generate a gas used in the first process, the second process gas supply unit  220  may generate a gas used in the second process, and the third process gas supply unit  230  may generate a gas used in the third process. 
     The electrode module  300  may include a high frequency power supply  310 , an electrode  320 , an ion blocker  330 , a shower head  340 , a heater ring  350 , and the like. The electrode module  300  may generate plasma using the gas provided from the gas supply device  200  and provide it to the processing space  501 . 
     A first space  301  may be formed between the electrode  320  and the ion blocker  330 , and a second space  302  may be formed between the ion blocker  330  and the shower head  340 . A processing space  501  may be formed under the shower head  340 . 
     The electrode  320  may be connected to the high frequency power supply  310 , and the ion blocker  330  may be connected to a constant voltage. The electrode  320  may include a plurality of supply holes. The first process gas supply unit  210  may provide the first process gas to the first space  301  through the electrode  320 . 
     The electromagnetic field generated between the electrode  320  and the ion blocker  330  may excite the first process gas to a plasma state. The first process gas excited into a plasma state (e.g., plasma effluent) may include radicals, ions, and/or electrons. The first process gas may vary depending on the target material. For example, when the target material includes silicon oxide formed on the substrate W, the first process gas may be nitrogen trifluoride (NF3), and may further include an inert gas (e.g., He). 
     The ion blocker  330  may include a conductive material and may have a disk shape. The ion blocker  330  may include a plurality of first through holes. In the plasma effluent, radicals may pass through the first through holes of the ion blocker  330 . On the other hand, the charged ions cannot pass through the first through holes of the ion blocker  330 . 
     The second process gas supply unit  220  may provide the second process gas to the ion blocker  330 , thereby providing the second process gas to the second space  302 . 
     The shower head  340  may include a conductive material and may have a disk shape. The shower head  340  may include a plurality of second through holes. The shower head  340  may provide a gas to the processing space  501  through the second through holes. 
     The third process gas supply unit  230  may provide the third process gas to a supply port formed in the shower head  340 , and through this, the third process gas may be provided to the second space  302 . 
     The heater ring  350  may be disposed between the ion blocker  330  and the shower head  340  and surround the second space  302 . The heater ring  350  may control the temperature of the shower head  340 . 
     In an embodiment of the present invention, the substrate W may be disposed on the substrate support unit  510 . However, depending on the process, the substrate W may be carried out from the substrate support unit  510 . 
     The exhaust device  100  may comprise a first vacuum pump  110 , a second vacuum pump  120 , a flow path  130 , a first valve  131 , a second valve  132 , a third valve  133 , and a fourth valve  134 . The exhaust device  100  may be disposed under the chamber  500  and may be directly connected to the chamber  500 . For example, the exhaust device  100  may be directly connected to the processing space  501  and the substrate support unit  510 . The exhaust device  100  may not be directly connected to the gas supply device  200  and the electrode module  300 . 
     While the exhaust device  100  performs a function of absorbing gas and discharging gas, the gas supply device  200  may perform a function of discharging gas without absorbing gas. That is, the exhaust device  100  and the gas supply device  200  may be separated from each other and perform different functions. 
     Here, the controller  400  may control overall operations of the exhaust device  100 , the gas supply device  200 , and the electrode module  300 . 
     The first vacuum pump  110  may exhaust gas or particles in the processing space  501  through the flow path  130 . For example, the flow path  130  connected to the first vacuum pump  110  may be connected to the first valve  131 , and the first valve  131  may be connected to the chamber  500 . When the first valve  131  is turned off, the first vacuum pump  110  cannot exhaust gas in the processing space  501 . When the first valve  131  is turned on, the first vacuum pump  110  may exhaust gas in the processing space  501  through the flow path  130 . Accordingly, the pressure of the processing space  501  may decrease from atmospheric pressure to a pressure close to 0 atm. Here, the first vacuum pump  110  may include a dry pump. 
     The second vacuum pump  120  may exhaust gas or particles in the processing space  501 . For example, the second vacuum pump  120  may be connected to the first vacuum pump  110  through the second valve  132 . Also, the second vacuum pump  120  may be connected to the chamber  500  through the third valve  133 . When the second valve  132  and the third valve  133  are turned on, the second vacuum pump  120  may exhaust gas in the processing space  501  through the flow path  130 . The gas exhaust of the second vacuum pump  120  may be performed later than that of the first vacuum pump  110 . The second vacuum pump  120  may make the pressure of the processing space  501  having a pressure close to 0 atm a vacuum. In this case, the second and third valves  132  and  133  may be turned on later than the first valve  131 . That is, after the first vacuum pump  110  operates, the second vacuum pump  120  may operate. The first vacuum pump  110  may exhaust gas, particles, etc. absorbed from the second vacuum pump  120 . Here, the second vacuum pump  120  may include a turbo molecular pump. 
     The fourth valve  134  may be disposed between the first vacuum pump  110  and the substrate support unit  510 . The fourth valve  134  may connect the first vacuum pump  110  and the substrate support unit  510 . For example, the fourth valve  134  may be connected to the first vacuum pump  110  through the flow path  130 , and may be connected to the flow path formed inside the substrate support unit  510 . Here, the flow path formed inside the substrate support unit  510  may be exposed in an upper portion of the substrate support unit  510 . That is, the flow path may be connected to a hole in an upper portion of the substrate support unit  510 . The hole in the upper portion of the substrate support unit  510  may directly contact the substrate W. That is, the flow path of the substrate support unit  510  may be formed between the substrate W and the fourth valve  134 . 
     When the fourth valve  134  is turned on, the first vacuum pump  110  may absorb the gas in the space between the substrate support unit  510  and the substrate W. That is, the first vacuum pump  110  may reduce the pressure of the flow path. Accordingly, the substrate support unit  510  may adsorb the substrate W, and the substrate W may be fixed to the substrate support unit  510 . Here, the fourth valve  134  may be turned on after the first to third valves  131  to  133  are turned on. That is, after the processing space  501  becomes vacuum, the fourth valve  134  may be turned on, and the first vacuum pump  110  may fix the substrate W to the substrate support unit  510 . However, the embodiment of the present invention is not limited thereto, and the operation order of the first to fourth valves  131  to  134  may be different from this. 
     When the fourth valve  134  is turned off, the first vacuum pump  110  may not absorb the gas in the space between the substrate support unit  510  and the substrate W. That is, the substrate support unit  510  may not adsorb the substrate W. Accordingly, the substrate W may not be fixed to the substrate support unit  510  and may be detached. 
     Accordingly, the substrate W may be fixed to the substrate support unit  510  during the process. Also, after completion of the process, the substrate W may be carried out without being fixed from the substrate support unit  510 . That is, even if no voltage is applied to the substrate support unit  510 , the substrate W may be fixed to the substrate support unit  510 . In addition, substrate processing apparatus  1  including the substrate support unit  510  having a simpler structure may be provided by fixing the substrate W to the substrate support unit  510  using the first vacuum pump  110  and the fourth valve  134 . 
     In addition, since the substrate W is fixed to the substrate support unit  510 , heat generated from the substrate support unit  510  may be transferred to the substrate W. That is, the substrate processing apparatus  1  including the substrate support unit  510  that improves the efficiency of heat transfer to the substrate W may be provided. 
     Hereinafter, the substrate support unit  510  will be described in more detail with reference to  FIGS.  2  to  5   . 
       FIG.  2    is a stereoscopic view of the substrate support unit of  FIG.  1   .  FIG.  3    is a cross-sectional view of the substrate support unit taken along line A-A of  FIG.  2   .  FIGS.  4  and  5    are top views of a substrate support unit in accordance with some embodiments. 
     Referring to  FIGS.  2  and  3   , the substrate support unit  510  may have a cylindrical shape. For example, the substrate support unit  510  may have a shape of a first cylinder connected to the chamber  500  and a second cylinder connected on the first cylinder. However, embodiments of the present invention are not limited thereto. 
     The substrate W may be disposed on the substrate support unit  510 . In this case, the substrate W may be connected to the flow path  511  of the substrate support unit  510 . The substrate support unit  510  may include a flow path  511  therein. The flow path  511  may correspond to a space between the fourth valve  134  and the substrate W. When the fourth valve  134  is turned on, the gas inside the flow path  511  may be exhausted to the outside by the first vacuum pump  110 . Accordingly, the pressure of the flow path  511  may be a vacuum, and the substrate W may be adsorbed to the substrate support unit  510 . 
     In this case, the flow path  511  may include a plurality of holes in the upper portion of the substrate support unit  510 . Referring to  FIG.  4   , the substrate support unit  510  may include a plurality of adsorption holes  512 . Here, the plurality of adsorption holes  512  may be scattered on the upper surface of the substrate support unit  510 . Accordingly, as the gas inside the adsorption hole  512  is exhausted, the substrate W may be adsorbed to the substrate support unit  510 . 
     Referring to  FIG.  5   , the substrate support unit  510  may include a plurality of adsorption holes  513 . Here, the plurality of adsorption holes  513  may have a plurality of concentric circles disposed on the upper surface of the substrate support unit  510 . As the gas inside the adsorption hole  513  is exhausted, the substrate W may be adsorbed to the substrate support unit  510 . 
     Hereinafter, an operation method of the substrate processing apparatus  1  will be described with reference to  FIGS.  6  to  9   . 
       FIG.  6    is a flowchart of a method of operating a substrate processing apparatus according to some embodiments.  FIGS.  7  to  9    are views for describing a method of operating a substrate processing apparatus according to some embodiments. 
     Referring to  FIGS.  6  and  7   , first and second vacuum pumps  110  and  120  may be turned on (S 600 ). At this time, the first to fourth valves  131  to  134  may be turned off. That is, the pressure of the processing space  501  may be maintained at atmospheric pressure. 
     Thereafter, the first valve  131  may be turned on (S 601 ). As the first valve  131  is turned on, the first vacuum pump  110  may absorb the gas in the processing space  501 . 
     Accordingly, the pressure in the processing space  501  may be close to 0 atm. 
     Thereafter, the second and third valves  132  and  133  may be turned on (S 602 ). As the second and third valves  132  and  133  are turned on, the second vacuum pump  120  may be connected to the first vacuum pump  110  and may absorb gas in the processing space  501 . The processing space  501  may be maintained in a vacuum state by the first vacuum pump  110  and the second vacuum pump  120 . 
     Thereafter, the substrate W may be mounted on the substrate support unit  510  (S 603 ). The transfer robot  530  may mount the substrate W on the substrate support unit  510 . In this case, the substrate W may directly contact the adsorption hole of the substrate support unit  510 . 
     Referring to  FIGS.  6  and  8   , the fourth valve  134  may be turned on (S 604 ). As the fourth valve  134  is turned on, the first vacuum pump  110  may absorb the gas in the substrate support unit  510 . Accordingly, the substrate W may be fixed to the substrate support unit  510 . In addition, heat generated from the substrate support unit  510  may be transferred to the substrate W. Accordingly, the position of the substrate W may be fixed during the process. 
     Thereafter, the gas supply device  200  and the electrode module  300  may operate (S 605 ). Accordingly, plasma generated in the first space  301  and the second space  302  may be provided to the processing space  501 . Accordingly, a processing process for the substrate W may be performed. 
     Referring to  FIGS.  6  and  9   , the process may be terminated (S 606 ). That is, the processing process for the substrate W may be terminated. 
     Subsequently, the fourth valve  134  may be turned off (S 607 ). Accordingly, the first vacuum pump  110  may not absorb the gas in the substrate support unit  510 . Accordingly, the space between the substrate support unit  510  and the substrate W cannot be maintained in a vacuum. Accordingly, the substrate W is not fixed to the substrate support unit  510 . At this time, the first to third valves  131  to  133  may maintain a turned-on state. That is, the processing space  501  may be maintained in a vacuum. 
     Subsequently, the substrate W may be carried out from the substrate support unit  510  (S 608 ). The transfer robot  530  may carry out the substrate W on the substrate support unit  510 . At this time, since the substrate W is not fixed to the substrate support unit  510 , it may be freely carried out. As described above, the substrate W may be fixed to the substrate support unit  510  through the first vacuum pump  110  and the fourth valve  134 . 
       FIG.  10    is a flowchart illustrating a method of operating a substrate processing apparatus according to another exemplary embodiment. 
     Referring to  FIGS.  1  and  10   , the first and second vacuum pumps  110  and  120  may be turned on (S 610 ). Thereafter, the first valve  131  may be turned on (S 611 ). Accordingly, the pressure in the processing space  501  may be close to 0 atm. At this time, the second to fourth valves  132  to  134  may be turned off. 
     Subsequently, the substrate W may be mounted on the substrate support unit  510  (S 612 ). Thereafter, the fourth valve  134  may be turned on (S 613 ). Accordingly, the substrate W may be fixed to the substrate support unit  510 . After the substrate W is fixed, the second and third valves  132  and  133  may be turned on (S 614 ). Accordingly, the second vacuum pump  120  may maintain the processing space  501  in a vacuum state. 
     Subsequently, the gas supply device  200  and the electrode module  300  may operate (S 615 ), and after the process ends (S 616 ), the fourth valve  134  may be turned off (S 617 ). Accordingly, the substrate W may not be fixed to the substrate support unit  510 . Subsequently, the substrate W may be carried out from the substrate support unit  510  (S 618 ). 
     Hereinafter, a substrate processing apparatus  1 ′ according to another exemplary embodiment will be described with reference to  FIG.  11   . Among the contents described above with reference to  FIGS.  1  to  10   , overlapping contents will be omitted. 
       FIG.  11    is a diagram of a substrate processing apparatus according to some embodiments. 
     Referring to  FIG.  11   , the exhaust device  100  may include a first vacuum pump  110 , a second vacuum pump  120 , a first valve  131 , a second valve  132 , a third valve  133  and a fourth valves  134 ′. 
     Here, the first valve  131  may connect the first vacuum pump  110  and the chamber  500 , and the second valve  132  may connect the first vacuum pump  110  and the second vacuum pump  120 . The third valve  133  may connect the second vacuum pump  120  and the chamber  500 . Also, the fourth valve  134 ′ may connect the second vacuum pump  120  and the substrate support unit  510 . 
     In this case, when the fourth valve  134 ′ is turned off, the substrate support unit  510  may not fix the substrate W. A space between the fourth valve  134 ′ and the substrate support unit  510  may not be maintained in a vacuum. 
     When the fourth valve  134 ′ is turned on, the second vacuum pump  120  may reduce the pressure in the space between the substrate support unit  510  and the substrate W. Accordingly, the substrate W may be fixed to the substrate support unit  510 . Unlike the substrate processing apparatus  1  described with reference to  FIGS.  1  to  10   , in which the first vacuum pump  110  reduces the pressure of the space between the substrate support unit  510  and the substrate W, the substrate processing apparatus  1 ′ described with reference to  FIG.  11    may fix the substrate W by the second vacuum pump  120 . That is, the substrate support unit  510  of the substrate processing apparatus  1 ′ may not be directly connected to the first vacuum pump  110 . 
     Hereinafter, a substrate processing apparatus  1 ″ according to another exemplary embodiment will be described with reference to  FIG.  12   . Among the contents described above with reference to  FIGS.  1  to  10   , overlapping contents will be omitted. 
       FIG.  12    is a diagram of a substrate processing apparatus according to some embodiments. 
     Referring to  FIG.  12   , the exhaust device  100  of the substrate processing apparatus  1 ″ may include a first vacuum pump  110 , a second vacuum pump  120 , a first valve  131 , a second valve  132 , a third valve  133 , a fifth valve  135 , and a sixth valve  136 . 
     Here, the fifth valve  135  may connect the first vacuum pump  110  and the substrate support unit  510 , and the sixth valve  136  may connect the second vacuum pump  120  and the substrate support unit  510 . Also, the fifth valve  135  and the sixth valve  136  may be connected to each other through a flow path. 
     When the fifth valve  135  is turned on, the first vacuum pump  110  may fix the substrate W to the substrate support unit  510 . When the fifth valve  135  is turned on, the second vacuum pump  120  may fix the substrate W to the substrate support unit  510 . When the fifth and sixth valves  135  and  136  are turned on, the first and second vacuum pumps  110  and  120  may fix the substrate W to the substrate support unit  510 . When both the fifth and sixth valves  135  and  136  are turned off, the first and second vacuum pumps  110  and  120  may fix the substrate W to the substrate support unit  510 . 
     In summary, when at least one of the fifth and sixth valves  135  and  136  is turned on, the substrate W may be fixed to the substrate support unit  510 . However, embodiments of the present invention are not limited thereto. 
     Although embodiments of the present invention have been described with reference to the above and the accompanying drawings, those skilled in the art, to which the present invention pertains, can understand that the present invention may be practiced in other specific forms without changing its technical spirit or essential features. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not limiting.