Abstract:
An inventive substrate treatment method is performed by a substrate treatment apparatus including a plate having an opposed surface to be kept in opposed spaced relation to one surface of a substrate for treating the substrate with a treatment liquid, and includes: a pre-supply liquid filling step of supplying a pre-supply liquid into a space defined between the one surface of the substrate and the plate through a spout which is provided in the opposed surface in opposed relation to the center of the substrate, and filling the space with the pre-supply liquid, the pre-supply liquid having a smaller contact angle with respect to the substrate and the plate than the treatment liquid; a treatment liquid replacing step of, after a liquid-filled state is established in the space filled with the pre-supply liquid, supplying the treatment liquid into the space to replace the pre-supply liquid present in the space with the treatment liquid while keeping the space in the liquid-filled state; and a treatment liquid contacting step of, after the replacement of the pre-supply liquid, filling the space with the treatment liquid to cause the treatment liquid to contact the one surface of the substrate.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a substrate treatment method and a substrate treatment apparatus. Exemplary substrates to be treated include semiconductor wafers, glass substrates for liquid crystal display devices, glass substrates for plasma display devices, glass substrates for FED (Field Emission Display) devices, substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks, substrates for photo masks, and ceramic substrates. 
         [0003]    2. Description of Related Art 
         [0004]    In production processes for semiconductor devices and liquid crystal display devices, a substrate treatment apparatus of a single substrate treatment type is often used for treating a surface of a substrate such as a semiconductor wafer or a glass substrate for a liquid crystal display panel with a treatment liquid. The substrate treatment apparatus includes, for example, a substrate holding member which generally horizontally holds the substrate, a plate to be opposed to the surface of the substrate held by the substrate holding member as being spaced a predetermined minute distance from the surface, and a spout provided in a surface of the plate opposed to the substrate for spouting the treatment liquid (see, for example, Japanese Unexamined Patent Publication No. 8-78368). The treatment liquid spouted from the spout is supplied into a space defined between the surface of the substrate and the plate, so that the space is filled with the treatment liquid. In order to fill the space between the surface of the substrate and the plate with the treatment liquid to establish a liquid-filled state in the space, the treatment liquid is brought into contact with the entire surface of the substrate. Thus, the surface of the substrate is treated with the treatment liquid. 
         [0005]    However, a gas-liquid interface is easily formed between the treatment liquid (e.g., deionized water) and air. Therefore, when the space between the surface of the substrate and the plate is filled with the treatment liquid, air originally present in the space is likely to be trapped in the space. As a result, air bubbles are liable to reside in the space filled with the treatment liquid. 
         [0006]    The air bubbles prevent the treatment liquid from contacting the surface of the substrate, so that the treatment does not proceed as desired on areas of the substrate on which the air bubbles reside. Therefore, the treatment with the treatment liquid is likely to unevenly proceed within a plane of the substrate. 
       SUMMARY OF THE INVENTION 
       [0007]    It is an object of the present invention to provide a substrate treatment method and a substrate treatment apparatus which ensure even treatment of one entire surface of a substrate with a treatment liquid while substantially preventing air from being trapped in a space filled with the treatment liquid on the substrate. 
         [0008]    A substrate treatment method according to the present invention is performed by a substrate treatment apparatus including a plate having an opposed surface to be kept in opposed spaced relation to one surface of a substrate for treating the substrate with a treatment liquid, the substrate treatment method including: a pre-supply liquid filling step of supplying a pre-supply liquid into a space defined between the one surface of the substrate and the plate through a spout which is provided in the opposed surface of the plate in opposed relation to the center of the substrate, and filling the space between the one surface of the substrate and the plate with the pre-supply liquid, the pre-supply liquid having a smaller contact angle with respect to the substrate and the plate than the treatment liquid; a treatment liquid replacing step of, after a liquid-filled state is established in the space filled with the pre-supply liquid, supplying the treatment liquid into the space between the one surface of the substrate and the plate to replace the pre-supply liquid present in the space with the treatment liquid while keeping the space in the liquid-filled state; and a treatment liquid contacting step of, after the replacement of the pre-supply liquid, filling the space with the treatment liquid to cause the treatment liquid to contact the one surface of the substrate. 
         [0009]    A substrate treatment apparatus according to the present invention is configured to treat a substrate with a treatment liquid, the apparatus including: a plate having an opposed surface to be kept in opposed spaced relation to one surface of the substrate and a spout provided in the opposed surface thereof; a pre-supply liquid supplying unit which supplies a pre-supply liquid to the spout, the pre-supply liquid having a smaller contact angle with respect to the substrate and the plate than the treatment liquid; a treatment liquid supplying unit which supplies the treatment liquid into a space defined between the one surface of the substrate and the plate; and a control unit which controls the pre-supply liquid supplying unit to fill the space with the pre-supply liquid to establish a liquid-filled state in the space, and controls the treatment liquid supplying unit to replace the pre-supply liquid present in the space with the treatment liquid to fill the space with the treatment liquid. 
         [0010]    Before the one surface of the substrate is brought into contact with the treatment liquid, the liquid-filled state is once established with the space between the one surface of the substrate and the plate being filled with the pre-supply liquid. Since the pre-supply liquid has a smaller contact angle with respect to the substrate and the plate than the treatment liquid, the substrate and the plate are properly wetted with the pre-supply liquid supplied into the space. Therefore, a gas-liquid interface is less liable to be formed between the pre-supply liquid and the ambient air, so that the air is relatively easily movable in the space. Accordingly, air originally present in the space is smoothly expelled from the space by the treatment liquid supplied into the space, so that virtually no air bubbles reside in the space after the liquid-filled state is established in the space filled with the pre-supply liquid. 
         [0011]    Thereafter, the pre-supply liquid present in the space is replaced with the treatment liquid with the space kept in the liquid-filled state. Then, the space is filled with the treatment liquid, whereby the substrate is treated with the treatment liquid. Since the pre-supply liquid is replaced with the treatment liquid with the space kept in the liquid-filled state, virtually no air bubbles reside in the space filled with the treatment liquid. Thus, the one entire surface of the substrate is evenly kept in contact with the treatment liquid and, therefore, evenly treated with the treatment liquid. 
         [0012]    Examples of the pre-supply liquid include alcohols such as IPA (isopropanol), ethanol and methanol, fluorine-containing solvents such as HFE (hydrofluoroether), and liquids containing surface-activation agents. 
         [0013]    The supply of the treatment liquid in the treatment liquid replacing step preferably continuously follows the supply of the pre-supply liquid in the pre-supply liquid filling step. In this case, the pre-supply liquid and the treatment liquid are sequentially supplied into the space. Thus, the space is kept in the liquid-filled state without trapping new air bubbles. 
         [0014]    The treatment liquid replacing step may include the step of supplying the treatment liquid into the space between the one surface of the substrate and the plate from the spout through a pipe through which the pre-supply liquid is supplied to the spout. In this case, the pre-supply liquid and the treatment liquid are supplied through the common pipe and spouted into the space, so that the pre-supply liquid is substantially prevented from remaining in the pipe. This prevents contamination of the substrate which may otherwise occur when the pre-supply liquid drips from the pipe. 
         [0015]    Further, the treatment liquid supplied into the space does not hinder liquid flow in the space, because the pre-supply liquid and the treatment liquid are supplied from the common spout. Thus, the space is kept in the liquid-filled state without trapping new air bubbles in the treatment liquid replacing step. 
         [0016]    At least a part of the plate to be opposed to the one surface of the substrate may be made of quartz. In this case, the plate is further wettable with the pre-supply liquid supplied into the space between the one surface of the substrate and the plate, because the quartz used as a material for at least the part of the plate opposed to the one surface of the substrate is hydrophilic. Thus, the air bubbles can be more reliably removed from the space. 
         [0017]    The foregoing and other objects, features and effects of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0018]      FIG. 1  is a sectional view schematically showing the construction of a substrate treatment apparatus according to one embodiment of the present invention; 
           [0019]      FIG. 2A  is a perspective view of a lower substrate holding member; 
           [0020]      FIG. 2B  is a plan view schematically showing the construction of the lower substrate holding member; 
           [0021]      FIG. 3  is a block diagram showing the electrical construction of the substrate treatment apparatus; 
           [0022]      FIG. 4  is a flow chart for explaining an exemplary treatment process to be performed by the substrate treatment apparatus; and 
           [0023]      FIGS. 5(   a ) to  5 ( d ) are diagrams for explaining the exemplary treatment process to be performed by the substrate treatment apparatus. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0024]      FIG. 1  is a sectional view schematically showing the construction of a substrate treatment apparatus according to one embodiment of the present invention. 
         [0025]    The substrate treatment apparatus is of a single substrate treatment type which treats front and back surfaces of a semiconductor wafer W as an exemplary substrate (hereinafter referred to simply as “wafer”) with a treatment liquid. The substrate treatment apparatus includes a lower substrate holding member  1  of a generally cylindrical bottomed shape for holding the wafer W, and an upper plate  2  of a disk shape opposed to the lower substrate holding member  1  above the lower substrate holding member  1 . A chemical agent and DIW (deionized water) are used as the treatment liquid for the treatment of the front and back surfaces of the wafer W. Examples of the chemical agent include hydrofluoric acid, buffered hydrofluoric acid (buffered HF, which is a liquid mixture of hydrofluoric acid and ammonium fluoride), SC1 (ammonia-hydrogen peroxide mixture), SC2 (hydrochloric acid/hydrogen peroxide mixture), SPM (sulfuric acid/hydrogen peroxide mixture) and polymer removing liquids. 
         [0026]      FIG. 2A  is a perspective view of the lower substrate holding member  1 , and  FIG. 2B  is a plan view schematically showing the construction of the lower substrate holding member  1 . Particularly,  FIG. 2A  illustrates the lower substrate holding member  1  with the wafer W being held thereon. 
         [0027]    Referring to  FIGS. 1 ,  2 A and  2 B, the lower substrate holding member  1  includes a lower plate portion  4  of a disk shape having a slightly greater diameter than the wafer W, an inner annular portion  5  of a generally cylindrical shape disposed adjacent the lower plate portion  4  as surrounding the lower plate portion  4 , an outer annular portion  6  of a generally cylindrical shape surrounding the inner annular portion  5 , and an annular connection portion  7  which connects a lower portion of the inner annular portion  5  to a lower portion of the outer annular portion  6 . 
         [0028]    The lower plate portion  4  has a lower substrate-opposed surface  9  to be opposed to a lower surface of the wafer W held on the lower plate portion  4 , and is disposed with its lower substrate-opposed surface  9  facing up. The lower substrate-opposed surface  9  is a generally flat horizontal surface. A plurality of support pins  8  (e.g., three support pins  8 ) for holding the wafer W are generally equidistantly disposed on a peripheral portion of the lower substrate-opposed surface  9 . The lower substrate-opposed surface  9  is opposed to the lower surface of the wafer W held by the plurality of support pins  8  as being spaced a predetermined distance P 1  (e.g., 0.5 mm to 2.0 mm) from the lower surface of the wafer W. The lower plate portion  4  is made of quartz. 
         [0029]    The inner annular portion  5  has a generally cylindrical shape coaxial with the center axis of a rotation shaft  10  to be described later. The inner annular portion  5  has an upper surface located at substantially the same height level as the wafer W held on the lower plate portion  4 . 
         [0030]    The outer annular portion  6  has a generally cylindrical shape coaxial with the center axis of the rotation shaft  10  to be described later. The outer annular portion  6  has an annular step  11  provided on an upper edge portion of an inner peripheral surface thereof between the inner and outer annular portions  5  and  6  for receiving a peripheral edge of the upper plate  2 . That is, the upper plate  2  is fitted in the annular step  11  to be thereby positioned in a treatment position to be described later. The bottom of the annular step  11  is located at a higher level than the upper surface of the inner annular portion  5 . 
         [0031]    A drain channel  14  for draining waste liquid such as waste chemical agent is provided on the connection portion  7 . The drain channel  14  is an annular channel which is coaxial with a rotation axis of the wafer W (the center axis of the rotation shaft  10  to be described later) and defined by an outer peripheral surface of the inner annular portion  5 , an inner peripheral surface of the outer annular portion  6  and an upper surface of the connection portion  7 . The connection portion  7  has a plurality of drain holes  12  (e.g., six drain holes  12 ) equidistantly provided circumferentially about the center axis of the rotation shaft  10  as vertically extending therethrough. Drain pipes  13  extending to a waste liquid treatment facility not shown are respectively connected to the drain holes  12 . The inner annular portion  5 , the outer annular portion  6  and the connection portion  7  are unitarily formed, for example, of polyvinyl chloride. 
         [0032]    The rotation shaft  10  extends vertically, and is connected to a lower surface of the lower plate portion  4 . A rotation force is inputted to the rotation shaft  10  from a motor  15 . 
         [0033]    Further, the rotation shaft  10  is hollow, and a lower surface treatment fluid supply pipe  16  is inserted in the rotation shaft  10 . The lower surface treatment fluid supply pipe  16  extends to the lower substrate-opposed surface  9  of the lower plate portion  4 , and communicates with a lower spout  17  which opens in a center portion of the lower substrate-opposed surface  9 . The lower surface treatment fluid supply pipe  16  is rotatable together with the rotation shaft  10 . The lower surface treatment fluid supply pipe  16  is connected to a stationary lower supply pipe  44  via a rotary joint not shown. The lower supply pipe  44  is connected to a lower chemical agent supply pipe  20 , a lower DIW supply pipe  21 , a lower IPA vapor supply pipe  22  and a lower liquid IPA supply pipe  45 . 
         [0034]    The chemical agent is supplied to the lower chemical agent supply pipe  20  from a chemical agent supply source. A lower chemical agent valve  23  for permitting and prohibiting the supply of the chemical agent is provided in the lower chemical agent supply pipe  20 . 
         [0035]    The DIW is supplied to the lower DIW supply pipe  21  from a DIW supply source. A lower DIW valve  24  for permitting and prohibiting the supply of the DIW is provided in the lower DIW supply pipe  21 . 
         [0036]    IPA vapor is supplied to the lower IPA vapor supply pipe  22  from an IPA vapor supply source. A lower IPA vapor valve  25  for permitting and prohibiting the supply of the IPA vapor is provided in the lower IPA vapor supply pipe  22 . 
         [0037]    Liquid IPA is supplied as a pre-supply liquid to the lower liquid IPA supply pipe  45  from a liquid IPA supply source. A lower liquid IPA valve  46  for permitting and prohibiting the supply of the liquid IPA is provided in the lower liquid IPA supply pipe  45 . 
         [0038]    When the lower chemical agent valve  23  is opened with the lower DIW valve  24 , the lower IPA vapor valve  25  and the lower liquid IPA valve  46  being closed, the chemical agent from the chemical agent supply source is supplied to the lower spout  17  through the lower chemical agent supply pipe  20 , the lower supply pipe  44  and the lower surface treatment fluid supply pipe  16 . When the lower DIW valve  24  is opened with the lower chemical agent valve  23 , the lower IPA vapor valve  25  and the lower liquid IPA valve  46  being closed, the DIW from the DIW supply source is supplied to the lower spout  17  through the lower DIW supply pipe  21 , the lower supply pipe  44  and the lower surface treatment fluid supply pipe  16 . When the lower IPA vapor valve  25  is opened with the lower chemical agent valve  23 , the lower DIW valve  24  and the lower liquid IPA valve  46  being closed, the IPA vapor from the IPA vapor supply source is supplied to the lower spout  17  through the lower IPA vapor supply pipe  22 , the lower supply pipe  44  and the lower surface treatment fluid supply pipe  16 . When the lower liquid IPA valve  46  is opened with the lower chemical agent valve  23 , the lower DIW valve  24  and the lower IPA vapor valve  25  being closed, the liquid IPA from the liquid IPA supply source is supplied to the lower spout  17  through the lower liquid IPA supply pipe  45 , the lower supply pipe  44  and the lower surface treatment fluid supply pipe  16 . 
         [0039]    The upper plate  2  has a disk shape having a greater diameter than the wafer W, and is made of quartz. The upper plate  2  has an upper substrate-opposed surface  19  to be opposed to the wafer W held on the lower plate portion  4 , and is disposed with its upper substrate-opposed surface  19  facing down. The upper substrate-opposed surface  19  is a flat horizontal surface. 
         [0040]    A rotation shaft  26  extending coaxially with the rotation shaft  10  is fixed to an upper surface of the upper plate  2 . The rotation shaft  26  is hollow, and an upper surface treatment fluid supply pipe  27  is inserted in the rotation shaft  26 . The upper surface treatment fluid supply pipe  27  extends to the upper substrate-opposed surface  19  of the upper plate  2 , and communicates with an upper spout  28  which opens in a center portion of the upper substrate-opposed surface  19 . 
         [0041]    The upper surface treatment fluid supply pipe  27  is rotatable together with the rotation shaft  26 . The upper surface treatment fluid supply pipe  27  is connected to a stationary upper supply pipe  43  via a rotary joint not shown. The upper supply pipe  43  is connected to an upper chemical agent supply pipe  30 , an upper DIW supply pipe  31 , an upper IPA vapor supply pipe  32  and an upper liquid IPA supply pipe  47 . 
         [0042]    The chemical agent is supplied to the upper chemical agent supply pipe  30  from the chemical agent supply source. An upper chemical agent valve  33  for permitting and prohibiting the supply of the chemical agent is provided in the upper chemical agent supply pipe  30 . 
         [0043]    The DIW is supplied to the upper DIW supply pipe  31  from the DIW supply source. An upper DIW valve  34  for permitting and prohibiting the supply of the DIW is provided in the upper DIW supply pipe  31 . 
         [0044]    The IPA vapor is supplied to the upper IPA vapor supply pipe  32  from the IPA vapor supply source not shown. An upper IPA vapor valve  35  for permitting and prohibiting the supply of the IPA vapor is provided in the upper IPA vapor supply pipe  32 . 
         [0045]    The liquid IPA is supplied to the upper liquid IPA supply pipe  47  from the liquid IPA supply source. An upper liquid IPA valve  48  for permitting and prohibiting the supply of the liquid IPA is provided in the upper liquid IPA supply pipe  47 . 
         [0046]    When the upper chemical agent valve  33  is opened with the upper DIW valve  34 , the upper IPA vapor valve  35  and the upper liquid IPA valve  48  being closed, the chemical agent from the chemical agent supply source is supplied to the upper spout  28  through the upper chemical agent supply pipe  30 , the upper supply pipe  43  and the upper surface treatment fluid supply pipe  27 . When the upper DIW valve  34  is opened with the upper chemical agent valve  33 , the upper IPA vapor valve  35  and the upper liquid IPA valve  48  being closed, the DIW from the DIW supply source is supplied to the upper spout  28  through the upper DIW supply pipe  31 , the upper supply pipe  43  and the upper surface treatment fluid supply pipe  27 . When the upper IPA vapor valve  35  is opened with the upper chemical agent valve  33 , the upper DIW valve  34  and the upper liquid IPA valve  48  being closed, the IPA vapor from the IPA vapor supply source is supplied to the upper spout  28  through the upper IPA vapor supply pipe  32 , the upper supply pipe  43  and the upper surface treatment fluid supply pipe  27 . When the upper liquid IPA valve  48  is opened with the upper chemical agent valve  33 , the upper DIW valve  34  and the upper IPA vapor valve  35  being closed, the liquid IPA from the liquid IPA supply source is supplied to the upper spout  28  through the upper liquid IPA supply pipe  47 , the upper supply pipe  43  and the upper surface treatment fluid supply pipe  27 . 
         [0047]    The rotation shaft  26  is supported from the above by a lift member  36  which is movable up and down. The rotation shaft  26  has an annular flange  37  provided on an outer peripheral surface thereof as projecting radially outward from an upper end portion thereof. The lift member  36  includes an annular support plate  38  which surrounds the rotation shaft  26  below the flange  37 . An inner peripheral edge of the support plate  38  has a smaller diameter than an outer peripheral edge of the flange  37 . The rotation shaft  26  is supported by the lift member  36  with an upper surface of the support plate  38  in engagement with a lower surface of the flange  37 . 
         [0048]    A lift driving mechanism  40  for moving up and down the lift member  36  is connected to the lift member  36 . By driving the lift driving mechanism  40 , the upper plate  2  fixed to the rotation shaft  26  is moved up and down between the treatment position at which the upper plate  2  fixed to the rotation shaft  26  is located in the vicinity of the upper surface of the wafer W held on the lower plate portion  4  (as indicated by a solid line in  FIG. 1 ) and a retracted position at which the upper plate  2  is significantly retracted above the lower plate portion  4  (as indicated by a two-dot-and-dash line in  FIG. 1 ). 
         [0049]    With the upper plate  2  moved down to the treatment position, the wafer W is treated with the treatment liquid. At the treatment position, the upper plate  2  is opposed to the upper surface of the wafer W held on the lower plate portion  4  as being spaced a predetermined distance P 2  (e.g., 1.0 mm) from the upper surface of the wafer W. 
         [0050]    When the lift driving mechanism  40  is driven to move down the upper plate  2  from the retracted position to the treatment position, the peripheral edge portion of the upper plate  2  is received by the annular step  11  of the outer annular portion  6 . When the lift member  36  is thereafter further moved down, the flange  37  is disengaged from the support member  38 . Thus, the rotation shaft  26  and the upper plate  2  are detached from the lift member  36  and supported by the lower substrate holding member  1 . Therefore, the upper plate  2  is rotatable together with the lower substrate holding member  1  at the treatment position. By inputting a rotative drive force to the rotation shaft  26  from the motor  15  with the wafer W being held on the lower plate portion  4 , the upper plate  2 , the lower plate portion  4  and the wafer W are rotated about a vertical axis. 
         [0051]      FIG. 3  is a block diagram showing the electrical construction of the substrate treatment apparatus. 
         [0052]    The substrate treatment apparatus includes a controller  50  including a microcomputer. 
         [0053]    The controller  50  is connected to the motor  15 , the lift driving mechanism  40 , the upper chemical agent valve  33 , the upper DIW valve  34 , the upper IPA vapor valve  35 , the lower chemical agent valve  23 , the lower DIW valve  24 , the lower IPA vapor valve  25 , and the like. 
         [0054]      FIG. 4  is a flow chart for explaining an exemplary treatment process to be performed by the substrate treatment apparatus.  FIGS. 5(   a ) to  5 ( d ) are diagrams for explaining the exemplary treatment process to be performed by the substrate treatment apparatus. In the substrate treatment process to be described below, a hydrophobic silicon wafer as an example of the wafer W is cleaned. 
         [0055]    The wafer W to be treated is loaded into the substrate treatment apparatus by a transport robot not shown, and held on the lower plate portion  4  of the lower substrate holding member  1  with its front surface facing up (Step S 1 ). When the wafer W is loaded, the upper plate  2  is located at the retracted position. 
         [0056]    With the wafer W being held on the lower plate portion  4 , the controller  50  drives the lift driving mechanism  40  to move down the upper plate  2  to the treatment position so that the upper substrate-opposed surface  19  is brought into opposed relation to the upper surface of the wafer W (Step S 2 ). 
         [0057]    After the upper plate  2  is moved down to the treatment position, the controller  50  opens the upper liquid IPA valve  48  and the lower liquid IPA valve  46  (Step S 3 ). Thus, the liquid IPA is supplied to the upper supply pipe  43  and the lower supply pipe  44  from the upper liquid IPA supply pipe  47  and the lower liquid IPA supply pipe  45 , respectively. The liquid IPA supplied into the upper supply pipe  43  is spouted from the upper spout  28  through the upper surface treatment fluid supply pipe  27 . Further, the liquid IPA supplied into the lower supply pipe  44  is spouted from the lower spout  17  through the lower surface treatment fluid supply pipe  16 . The liquid IPA has a relatively small contact angle with respect to a silicon material and a quartz material (i.e., the liquid IPA has a smaller contact angle with respect to the silicon material and the quartz material than the chemical agent and the DIW). The liquid IPA from the upper spout  28  is supplied to an upper treatment space  41  defined between the upper surface of the wafer W and the upper substrate-opposed surface  19  of the upper plate  2 , and spread radially from the upper spout  28  in the upper treatment space  41 . Further, the liquid IPA from the lower spout  17  is supplied to a lower treatment space  42  defined between the lower surface of the wafer W and the lower substrate-opposed surface  9  of the lower plate portion  4 , and spread radially from the lower spout  17  in the lower treatment space  42  (see  FIG. 5(   a )). The wafer W, the upper plate  2  and the lower plate portion  4  are properly wetted with the liquid IPA supplied to the upper treatment space  41  and the lower treatment space  42 , because the liquid IPA has a relatively small contact angle with respect to the wafer W, the upper plate  2  and the lower plate portion  4 . Particularly, the upper plate  2  and the lower plate portion  4  which are each made of the hydrophilic quartz are more wettable with the liquid IPA. Accordingly, a gas-liquid interface is less liable to be formed between the liquid IPA and the ambient air, so that the air has a relatively high mobility in the upper treatment space  41  and the lower treatment space  42 . Therefore, air originally present in the upper treatment space  41  and the lower treatment space  42  is expelled from the spaces  41 ,  42  by the liquid IPA supplied into the upper treatment space  41  and the lower treatment space  42 . 
         [0058]    The liquid IPA is continuously spouted from the upper spout  28  and the lower spout  17 , whereby a space defined between the upper plate  2  and the lower plate portion  4  is filled with the liquid IPA. Thus, a liquid-filled state is established in the upper treatment space  41  and the lower treatment space  42  filled with the liquid IPA (see  FIG. 5(   b )). Virtually no air bubbles are present in the upper treatment space  41  and the lower treatment space  42  which are filled with the liquid IPA to be kept in the liquid-filled state. 
         [0059]    After a lapse of a predetermined IPA treatment period (e.g., 1 to 10 seconds) during which the upper treatment space  41  and the lower treatment space  42  are filled with the liquid IPA to be kept in the liquid-filled state (YES in Step S 4 ), the controller  50  closes the upper liquid IPA valve  48  and the lower liquid IPA valve  46 , and opens the upper chemical agent valve  33  and the lower chemical agent valve  23  (Step S 5 ). Thus, the supply of the liquid IPA to the upper supply pipe  43  is stopped, and the chemical agent is supplied into the upper supply pipe  43  from the upper chemical agent supply pipe  30 . Further, the supply of the liquid IPA to the lower supply pipe  44  is stopped, and the chemical agent is supplied into the lower supply pipe  44  from the lower chemical agent supply pipe  20 . At this time, the upper chemical agent valve  33  and the lower chemical agent valve  23  are opened generally simultaneously with the closing of the upper liquid IPA valve  48  and the lower liquid IPA valve  46 . Therefore, the upper treatment space  41  and the lower treatment space  42  are still kept in the liquid-filled state during the switching from the liquid IPA to the chemical agent. 
         [0060]    The chemical agent supplied to the upper supply pipe  43  is spouted from the upper spout  28  through the upper surface treatment fluid supply pipe  27  (see  FIG. 5(   c )). The chemical agent supplied to the upper treatment space  41  from the upper spout  28  is mixed with the liquid IPA and spread in the upper treatment space  41  kept in the liquid-filled state. Further, the chemical agent supplied to the lower supply pipe  44  is spouted from the lower spout  17  through the lower surface treatment fluid supply pipe  16  (see  FIG. 5(   c )). The chemical agent supplied into the lower treatment space  42  from the lower spout  17  is mixed with the liquid IPA and spread in the lower treatment space  42  kept in the liquid-filled state. 
         [0061]    Then, the liquid IPA present in the upper treatment space  41  and the lower treatment space  42  is gradually replaced with the chemical agent with the upper treatment space  41  and the lower treatment space  42  kept in the liquid-filled state. As a result, the concentrations of the chemical agent in the liquid IPA in the upper treatment space  41  and the lower treatment space  42  are increased. As the chemical agent is supplied into the upper treatment space  41  and the lower treatment space  42 , the spaces  41 ,  42  are filled with the chemical agent and, finally, the liquid-filled state is established in the upper treatment space  41  and the lower treatment space  42 . 
         [0062]    The chemical agent is spouted into the upper treatment space  41  through the pipes  43 ,  27  through which the liquid IPA has flowed, and spouted into the lower treatment space  42  through the pipes  44 ,  16  through which the liquid IPA has flowed. Therefore, the liquid IPA is prevented from remaining in the upper supply pipe  43 , the upper surface treatment fluid supply pipe  27 , the lower supply pipe  44  and the lower surface treatment fluid supply pipe  16 . This prevents the contamination of the wafer W with the liquid IPA which may otherwise occur when the liquid IPA is dripped from the pipes  43 ,  27 ,  44 ,  16  toward the wafer W. 
         [0063]    Since the chemical agent is spouted into the upper treatment space  41  and the lower treatment space  42  from the upper spout  28  and the lower spout  17 , respectively, from which the liquid IPA has been spouted, there is virtually no possibility that the chemical agent supplied into the spaces  41 ,  42  prevents the flow of the liquid IPA in the spaces  41 ,  42 . 
         [0064]    Thereafter, the chemical agent is continuously spouted from the upper spout  28  and the lower spout  17 , whereby the upper treatment space  41  and the lower treatment space  42  are kept filled with the chemical agent. Thus, the upper and lower surfaces of the wafer W are kept in contact with the chemical agent, and cleaned with the chemical agent (see  FIG. 5(   d )). The chemical agent overflows from the upper treatment space  41  and the lower treatment space  42 , and is drained to the waste liquid treatment facility not shown sequentially through a space defined between the upper substrate-opposed surface  19  of the upper plate  2  and the upper surface of the inner annular portion  5 , the drain channel  14 , the drain holes  12  and the drain pipes  13 . 
         [0065]    The upper treatment space  41  and the lower treatment space  42  are relatively narrow. Therefore, the upper treatment space  41  and the lower treatment space  42  can be filled with a smaller amount of the chemical agent. This reduces the consumption of the chemical agent. 
         [0066]    After a lapse of a predetermined chemical agent treatment period (e.g., 30 seconds) (YES in Step S 6 ), the controller  50  closes the upper chemical agent valve  33  and the lower chemical agent valve  23  to stop the supply of the chemical agent from the upper spout  28  and the lower spout  17  (Step S 7 ). 
         [0067]    Then, the controller  50  opens the upper DIW valve  34  and the lower DIW valve  24  to spout the DIW from the upper spout  28  and the lower spout  17  (Step S 8 ). Thus, the chemical agent present in the upper treatment space  41  and the lower treatment space  42  is gradually replaced with the DIW with the upper treatment space  41  and the lower treatment space  42  kept in the liquid-filled state. Finally, the upper treatment space  41  and the lower treatment space  42  are filled with the DIW. 
         [0068]    Thereafter, the DIW is continuously spouted from the upper spout  28  and the lower spout  17 , whereby the upper treatment space  41  and the lower treatment space  42  are kept filled with the DIW. Thus, the upper and lower surfaces of the wafer W are kept in contact with the DIW, so that the chemical agent adhering to the upper and lower surfaces of the wafer W is rinsed away with the DIW. The DIW overflows from the upper treatment space  41  and the lower treatment space  42 , and is drained to the waste liquid treatment facility not shown sequentially through the space between the upper substrate-opposed surface  19  of the upper plate  2  and the upper surface of the inner annular portion  5 , the drain channel  14 , the drain holes  12  and the drain pipes  13 . 
         [0069]    After a lapse of a predetermined rinsing period (e.g., 60 seconds) (YES in Step S 9 ), the controller  50  closes the upper DIW valve  34  and the lower DIW valve  24  to stop the supply of the DIW from the upper spout  28  and the lower spout  17  (Step S 10 ). 
         [0070]    Then, the controller  50  opens the upper IPA vapor valve  35  and the lower IPA vapor valve  25  to spout the IPA vapor from the upper spout  28  and the lower spout  17  (Step S 11 ). Further, the controller  50  controls the motor  15  to rotate the wafer W at a predetermined drying speed (e.g., a higher speed on the order of 2500 rpm) (Step S 11 ). Thus, the DIW adhering to the upper and lower surfaces of the wafer W is spun off by a centrifugal force, whereby the wafer W is dried. 
         [0071]    In this drying step, the upper substrate-opposed surface  19  of the upper plate  2  and the lower substrate-opposed surface  9  of the lower plate portion  4  are closely opposed to the upper and lower surfaces of the wafer W, respectively, so that the upper and lower surfaces of the wafer W are isolated from the external atmosphere. By supplying the IPA vapor to the upper treatment space  41  and the lower treatment space  42 , the DIW adhering to the upper and lower surfaces of the wafer W is replaced with IPA, and the upper and lower surfaces of the wafer W are dried due to the volatility of the IPA vapor. Thus, the upper and lower surfaces of the wafer W are quickly dried with no DIW mark left on the lower surface of the wafer W in the drying step. 
         [0072]    After a lapse of a predetermined drying period (e.g., 30 seconds) (YES in Step S 12 ), the controller  50  controls the motor  15  to stop the rotation of the lower substrate holding member  1 , and closes the upper IPA vapor valve  35  and the lower IPA vapor valve  25  to stop the supply of the IPA vapor from the upper spout  28  and the lower spout  17  (Step S 13 ). 
         [0073]    After the rotation of the lower substrate holding member  1  is stopped, the controller  50  drives the lift driving mechanism  40  to move up the upper plate  2  toward the retracted position (Step S 14 ). Thereafter, the treated wafer W is unloaded by the transport robot not shown (Step S 15 ). 
         [0074]    According to this embodiment, as described above, the liquid-filled state is once established in the upper treatment space  41  and the lower treatment space  42  filled with the liquid IPA before the chemical agent is supplied to the wafer W. The wafer W, the upper plate  2  and the lower plate portion  4  are properly wetted with the liquid IPA supplied into the upper treatment space  41  and the lower treatment space  42 , because the liquid IPA has a relatively small contact angle with respect to the wafer W, the upper plate  2  and the lower plate portion  4 . Therefore, a gas-liquid interface is less liable to be formed between the liquid IPA and the ambient air, so that the air has a relatively high mobility in the upper treatment space  41  and the lower treatment space  42 . Accordingly, the air present in the upper treatment space  41  and the lower treatment space  42  is expelled by the liquid IPA supplied into the spaces  41 ,  42 , so that virtually no air bubbles are present in the upper treatment space  41  and the lower treatment space  42  kept in the liquid-filled state. 
         [0075]    With the upper treatment space  41  and the lower treatment space  42  kept in the liquid-filled state, the liquid IPA present in the spaces  41 ,  42  is replaced with the chemical agent. Thus, the upper treatment space  41  and the lower treatment space  42  are filled with the chemical agent, whereby the wafer W is treated with the chemical agent. Since the upper treatment space  41  and the lower treatment space  42  are kept in the liquid-filled state during the replacement of the liquid IPA with the chemical agent, virtually no air bubbles are present in the spaces  41 ,  42  filled with the chemical agent. Thus, the entire upper and lower surfaces of the wafer W are evenly kept in contact with the chemical agent and, therefore, evenly treated with the chemical agent. 
         [0076]    Further, the upper plate  2  and the lower plate portion  4  are made of the hydrophilic quartz and, therefore, further wettable with the liquid IPA supplied into the upper treatment space  41  and the lower treatment space  42 . Thus, the air bubbles are reliably removed from the upper treatment space  41  and the lower treatment space  42 . 
         [0077]    While one embodiment of the present invention has thus been described, the invention may be embodied in other ways. In the embodiment described above, the liquid IPA is used as the pre-supply liquid by way of example. Instead of the liquid IPA, an alcohol solvent such as ethanol or methanol may be used as the pre-supply liquid. Alternatively, a fluorine-containing solvent such as HFE (hydrofluoroether) or a liquid containing a surface active agent may be used as the pre-supply liquid. 
         [0078]    Where liquid HFE is used as the pre-supply liquid, the upper treatment space  41  and the lower treatment space  42  are first filled with the liquid HFE to be kept in the liquid-filled state. When the chemical agent is supplied into the upper treatment space  41  and the lower treatment space  42  from the upper spout  28  and the lower spout  17 , the chemical agent does not intermingle with the liquid HFE, but pushes out the liquid HFE to spread in the spaces  41 ,  42 . Then, the upper treatment space  41  and the lower treatment space  42  are filled with the chemical agent. 
         [0079]    Further, the liquid IPA present in the upper treatment space  41  and the lower treatment space  42  may be replaced with the DIW but not with the chemical agent. In this case, the chemical agent is supplied into the upper treatment space  41  and the lower treatment space  42  after the replacement with the DIW, whereby the spaces  41 ,  42  are filled with the chemical agent. Thus, the wafer W is treated with the chemical agent. 
         [0080]    In the embodiment described above, the chemical agent and the DIW are used as the treatment liquid by way of example. However, only the DIW may be used as the treatment liquid. In this case, the DIW is used instead of the chemical agent in Steps S 5  to S 7 , and Steps S 8  to S 10  for the rinsing may be omitted. Not only the DIW but also functional water such as carbonated water, ionized water, ozonized water, reductive water (hydrogen water) or magnetic water may be used as the treatment liquid. 
         [0081]    During the supply of the liquid IPA, at least one of the upper plate  2  and the lower plate portion  4  may be rotated. Thus, even if air bubbles are present in the upper treatment space  41  and the lower treatment space  42 , the air bubbles can be removed. 
         [0082]    The material for the upper plate  2  and the lower plate portion  4  is not limited to the hydrophilic quartz, but may be a hydrophobic material such as polyvinyl chloride. Even in this case, the upper treatment space  41  and the lower treatment space  42  are filled with the pre-supply liquid such as the liquid IPA to be kept in the liquid-filled state before the supply of the treatment liquid, whereby the contact angle with respect to the surfaces of the upper plate  2  and the lower plate portion  4  is reduced. Therefore, the air bubbles present in the spaces  41 ,  42  can be removed by a centrifugal force. 
         [0083]    While the present invention has been described in detail by way of the embodiment thereof, it should be understood that the embodiment is merely illustrative of the technical principles of the present invention but not limitative of the invention. The spirit and scope of the present invention are to be limited only by the appended claims. 
         [0084]    This application corresponds to Japanese Patent Application No. 2007-281985 filed in the Japanese Patent Office on Oct. 30, 2007, the disclosure of which is incorporated herein by reference in its entirety.