Abstract:
An exposure apparatus for exposing a substrate to exposure light via a pattern of a mask. The apparatus includes a stage configured to hold one of the substrate and the mask, and to move, a projection optical system configured to project the pattern onto the substrate, a defining member facing the stage and configured to define a space, between the stage and the projection optical system, through which the exposure light passes and which is to be filled with fluid, a first stream mechanism having a first supply port in the defining member and configured to stream the fluid through the space from the first supply port, an exhaust mechanism having an exhaust port in the defining member and configured to exhaust fluid in the space from the exhaust port, and a second stream mechanism having a second supply port different from the first supply port. The second supply port is arranged to surround the space at a lower portion of the defining member, and configured to stream fluid from the second supply port against the stage to seal the space.

Description:
[0001]     This application is a divisional application of copending U.S. patent application Ser. No. 11/136,687, filed May 25, 2005, which is a divisional of U.S. patent application Ser. No. 10/329,816, filed on Dec. 27, 2002, which issued as U.S. Pat. No. 6,934,003 on Aug. 23, 2005. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to an exposure apparatus which projects and transfers a pattern formed on a mask to a substrate using exposure light, and a device manufacturing method.  
       BACKGROUND OF THE INVENTION  
       [0003]     In photolithography for manufacturing a semiconductor element, or the like, an exposure apparatus which projects and exposes a pattern image on a mask (e.g., a reticle) to a photosensitive substrate through a projecting optical system is used. Semiconductor integrated circuits developed recently are aiming at micropatterning. In photolithography, photolithography light sources are going to have shorter wavelengths.  
         [0004]     However, when vacuum UV light and, more particularly, light having a wavelength shorter than 250 nm, e.g., harmonic light of a KrF excimer laser (wavelength: 248 nm), an ArF excimer laser (wavelength: 193 nm), F 2  laser (wavelength: 157 nm), or a YAG laser is used as exposure light, the intensity of exposure light decreases due to the influence of exposure light absorption by oxygen, and the like.  
         [0005]     To avoid the decrease in exposure light transmittance, a conventional exposure apparatus having a light source such as an F 2  excimer laser forms a sealed space where only an optical path portion is sealed and replaces the gas in the sealed space with a gas such as nitrogen containing no oxygen.  
         [0006]      FIGS. 14A and 14B  are views showing an exposure apparatus which performs exposure by supplying an inert gas to a space between a photosensitive substrate (wafer) and the final optical member of a projecting optical system (lens barrel) to form an inert gas atmosphere in the space, In this exposure apparatus, to separate the space on the exposure region from the ambient atmosphere, a shielding member is arranged around the space, and the inert gas is supplied from the periphery of the exposure region into the space.  
         [0007]     In the exposure apparatus shown in  FIGS. 14A and 14B , however, the atmosphere in the space cannot be replaced with the inert gas until the atmosphere at the step or gap around the wafer moves into the space. In exposing the periphery of the wafer, the inert gas concentration in the space decreases. In addition, when the wafer stage moves at a high speed, the inert gas concentration decreases due to the influence of involvement, resulting in a variation in illuminance.  
         [0008]     A similar problem is posed when an inert gas is supplied to the periphery of a reticle. In exposing the periphery of the reticle, the inert gas concentration in the space decreases. In addition, when the wafer stage moves at a high speed, the inert gas concentration decreases due to the influence of involvement, resulting in a variation in illuminance.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention has been made in consideration of the above problems, and has as its object to provide an exposure apparatus which can stabilize the inert gas concentration in a container that accommodates various members including an illumination system, a projecting lens system, and mechanical members, and a device manufacturing method.  
         [0010]     According to the present invention, the foregoing object is attained by providing an exposure apparatus which projects and transfers a pattern formed on a mask to a substrate using exposure light, comprising:  
         [0011]     a stage;  
         [0012]     an optical system;  
         [0013]     a gas stream forming mechanism which forms a stream of an inert gas in an optical path space including a space which is located between the stage and the optical system and through which the exposure light passes; and  
         [0014]     a member which is arranged between the stage and a portion around the gas stream forming mechanism to form a predetermined space that maintains an average inert gas concentration P satisfying 
        P 2 &lt;P&lt;P 1  
 
 where P 1  is an average concentration of the inert gas present in the optical path space, and P 2  is an average concentration of the inert gas present outside the optical path space. 
       
 
         [0016]     According to the present invention, the foregoing object is attained by providing an exposure apparatus which projects and transfers a pattern formed on a mask to a substrate using exposure light, comprising:  
         [0017]     a stage;  
         [0018]     an optical system;  
         [0019]     a gas stream forming mechanism which forms a stream of an inert gas in an optical path space including a space which is located between the stage and the optical system and through which the exposure light passes; and  
         [0020]     a member which forms a predetermined space between the optical path space and a peripheral space outside the optical path space in the exposure apparatus,  
         [0021]     wherein a width of the member in a direction of the stream of the inert gas is not less than twice a distance between the member and the stage.  
         [0022]     In a preferred embodiment, the member is formed around the optical path space.  
         [0023]     In a preferred embodiment, the member has at least one of a groove arranged outside the optical path space to surround the optical path space.  
         [0024]     In a preferred embodiment, the width of the member in the direction of the stream of the inert gas is not less than three times the distance between the member and the stage.  
         [0025]     In a preferred embodiment, the member is arranged upstream of the gas stream with respect to the optical path space.  
         [0026]     In a preferred embodiment,  
         [0027]     the apparatus performs exposure while scanning the mask and the substrate, and  
         [0028]     the member is arranged in a direction of scanning with respect to the optical path space.  
         [0029]     In a preferred embodiment, the member has a concave portion at a portion against the stage on an upstream side of the gas stream in the optical path space.  
         [0030]     In a preferred embodiment, the apparatus further comprises a supply port which supplies an inert gas to the predetermined space, wherein the supply port is arranged on an upstream side of the gas stream in the optical path space.  
         [0031]     In a preferred embodiment, the member is formed around the optical path space.  
         [0032]     In a preferred embodiment, the member has at least one of a groove arranged outside the optical path space to surround the optical path space.  
         [0033]     According to the present invention, the foregoing object is attained by providing an exposure apparatus which projects and transfers a pattern formed on a mask to a substrate using exposure light, comprising:  
         [0034]     a stage;  
         [0035]     an optical system;  
         [0036]     a gas stream forming mechanism which forms a stream of an inert gas in an optical path space including a space which is located between the stage and the optical system and through which the exposure light passes; and  
         [0037]     a member which forms a predetermined space between the optical path space and a peripheral space outside the optical path space in the exposure apparatus,  
         [0038]     wherein a distance between the member and the stage is shorter than that between the stage and an optical element of the optical system, which is closest to the stage.  
         [0039]     In a preferred embodiment, the distance between the member and the stage is not more than one-half that between the stage and the optical element of the optical system, which is closest to the stage.  
         [0040]     In a preferred embodiment, the distance between the member and the stage is not more than one-quarter that between the stage and the optical element of the optical system, which is closest to the stage.  
         [0041]     In a preferred embodiment, the member is arranged upstream of the gas stream with respect to the optical path space.  
         [0042]     In a preferred embodiment, the apparatus performs exposure while scanning the mask and the substrate, and  
         [0043]     the member is arranged in a direction of scanning with respect to the optical path space.  
         [0044]     In a preferred embodiment, the member has a concave portion at a portion against the stage on an upstream side of the gas stream in the optical path space.  
         [0045]     In a preferred embodiment, the apparatus further comprises a supply port which supplies an inert gas to the predetermined space, wherein the supply port is arranged on an upstream side of the gas stream in the optical path space.  
         [0046]     In a preferred embodiment, the member is formed around the optical path space.  
         [0047]     In a preferred embodiment, the member has at least one of a groove arranged outside the optical path space to surround the optical path space.  
         [0048]     According to the present invention, the foregoing object is attained by providing an exposure apparatus which projects and transfers a pattern formed on a mask to a substrate using exposure light, comprising:  
         [0049]     a stage;  
         [0050]     an optical system;  
         [0051]     a gas stream forming mechanism which forms a stream of an inert gas in an optical path space including a space which is located between the stage and the optical system and through which the exposure light passes;  
         [0052]     a member which forms a predetermined space between the optical path space and a peripheral space outside the optical path space in the exposure apparatus; and  
         [0053]     a gas supply mechanism which supplies the inert gas into the predetermined space.  
         [0054]     In a preferred embodiment, the gas supply mechanism is branched from the gas stream forming mechanism.  
         [0055]     In a preferred embodiment, a position at which the gas supply mechanism supplies the inert gas into the predetermined space is located upstream of the gas stream in the predetermined space with respect to the optical path space.  
         [0056]     In a preferred embodiment, the apparatus performs exposure while scanning the mask and the substrate, and  
         [0057]     the member is arranged in a direction of scanning with respect to the optical path space.  
         [0058]     In a preferred embodiment, the member has a concave portion at a portion against the stage on an upstream side of the gas stream in the optical path space.  
         [0059]     In a preferred embodiment, the apparatus further comprises a supply port which supplies an inert gas to the predetermined space, wherein the supply port is arranged on an upstream side of the gas stream in the optical path space.  
         [0060]     In a preferred embodiment, the member is arranged upstream of the gas stream with respect to the optical path space.  
         [0061]     In a preferred embodiment, the member is formed around the optical path space.  
         [0062]     In a preferred embodiment, the member has at least one of a groove arranged outside the optical path space to surround the optical path space.  
         [0063]     According to the present invention, the foregoing object is attained by providing an exposure apparatus which projects and transfers a pattern formed on a mask to a substrate using exposure light, comprising:  
         [0064]     a stage;  
         [0065]     an optical system;  
         [0066]     a gas stream forming mechanism which supplies an inert gas into an optical path space including a space which is located between the stage and the optical system and through which the exposure light passes; and  
         [0067]     a member which forms a predetermined space between the optical path space and a peripheral space outside the optical path space in the exposure apparatus,  
         [0068]     wherein the member forms, in the predetermined space, at least one groove having a width in a direction of a stream of the inert gas.  
         [0069]     In a preferred embodiment, the apparatus further comprises a gas supply mechanism which supplies the inert gas from the at least one groove.  
         [0070]     In a preferred embodiment, the member has a plurality of partitioning members arranged to surround the optical path space.  
         [0071]     The distance from the lower end of the partitioning members to the substrate is preferably substantially equal to the distance from the lower end of the shielding member of the gas stream forming mechanism to the substrate.  
         [0072]     The lower surface of the member preferably has at least one groove along the outer periphery of the optical path space.  
         [0073]     The groove preferably becomes deeper as it is separated from the center of the gas stream forming mechanism.  
         [0074]     The supply port and exhaust port of the gas stream forming mechanism and their channel are preferably formed in the member.  
         [0075]     The member preferably has inside an opening which extends from the gas channel to the groove.  
         [0076]     Part of the shielding member preferably has an opening.  
         [0077]     The exhaust amount of the gas in the gas stream forming mechanism is preferably smaller than the supply amount of the gas.  
         [0078]     The apparatus preferably further comprises an exhaust unit which exhausts the inert gas that leaks from the gas stream forming mechanism through the predetermined space together with the ambient atmosphere.  
         [0079]     The inert gas can be nitrogen gas or helium gas.  
         [0080]     The gas stream forming mechanism is preferably arranged to form the stream of the inert gas in the optical path space between the projecting optical system and the substrate. The member is preferably arranged to form the predetermined space between the stage and a portion around the gas stream forming mechanism.  
         [0081]     The gas stream forming mechanism is preferably arranged to form the stream of the inert gas in the optical path space between an illumination optical system which illuminates the mask and a mask stage which holds the mask. The member is preferably arranged to form the predetermined space between the stage and a portion around the gas stream forming mechanism.  
         [0082]     The gas stream forming mechanism is preferably arranged to form the stream of the inert gas in the optical path space between the projecting optical system and a mask stage which holds the mask. The member is preferably arranged to form the predetermined space between the stage and a portion around the gas stream forming mechanism.  
         [0083]     The gas stream forming mechanism may have a first gas stream forming mechanism which is arranged to form the stream of the inert gas in a first optical path space between the projecting optical system and the substrate, a second gas stream forming mechanism which is arranged to form the stream of the inert gas in a second optical path space between the illumination system which illuminates the mask and the mask stage which holds the mask, and a third gas stream forming mechanism which is arranged to form the stream of the inert gas in a third optical path space between the mask stage and the projecting optical system. The member may be arranged to form the predetermined space between the stage and portions around the first to third gas stream forming mechanisms.  
         [0084]     The supply port and exhaust port of the gas stream forming mechanism and their channel may be formed in the member.  
         [0085]     The inert gas may be supplied from the member to the substrate. Supply of the inert gas from the member to the substrate and supply of the inert gas into the optical path space are preferably independently or commonly performed. The lower portion of the member preferably has at least one groove.  
         [0086]     An exposure apparatus which projects and transfers a pattern formed on a mask to a substrate using exposure light preferably comprises:  
         [0087]     a stage;  
         [0088]     an optical system;  
         [0089]     a gas stream forming mechanism which supplies an inert gas into an optical path space including a space between the stage and the optical system where the exposure light passes through,  
         [0090]     wherein the gas stream forming mechanism comprises a restricting member in the optical path space in a direction from the optical system to the substrate.  
         [0091]     The gas stream forming mechanism may have two opposing supply ports at a position close to the optical system in the optical path space, and a supply port and an exhaust port opposing each other at a position close to the substrate in the optical path space, and  
         [0092]     the restricting member may be installed between the two pairs of supply/exhaust ports in a direction substantially along a gas stream.  
         [0093]     The gas stream forming mechanism may have a supply port and an exhaust port opposing each other at a position close to the optical system in the local space, and the restricting member may be a plate member installed on the substrate side of the supply port outlet or exhaust port inlet in a direction almost along the gas stream. Alternatively, the gas stream forming mechanism may have two opposing supply ports at a position close to the optical system in the local space, and the restricting member may be a plate member installed on the substrate side of the supply port outlet in a direction almost along the gas stream.  
         [0094]     As a device manufacturing method using the above-described exposure apparatus, the following methods are also incorporated in the present invention. A device manufacturing method comprises the steps of exposing a substrate using the above exposure apparatus, and developing the exposed substrate.  
         [0095]     Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0096]      FIG. 1  is a view showing part of an exposure apparatus according to the first embodiment of the present invention;  
         [0097]      FIG. 2  is a view showing a modification of the exposure apparatus shown in  FIG. 1  according to the first embodiment of the present invention;  
         [0098]      FIG. 3  is a view showing another modification of the exposure apparatus shown in  FIG. 1  according to the first embodiment of the present invention;  
         [0099]      FIG. 4  is a view showing the modification in  FIG. 3  viewed from the lower side;  
         [0100]      FIG. 5  is a view showing part of an exposure apparatus according to the second embodiment of the present invention;  
         [0101]      FIG. 6  is a view showing a modification of the exposure apparatus shown in  FIG. 5  according to the second embodiment of the present invention;  
         [0102]      FIG. 7  is a view showing part of another exposure apparatus according to the second embodiment of the present invention;  
         [0103]      FIG. 8  is a view showing part of an exposure apparatus according to the third embodiment of the present invention;  
         [0104]      FIG. 9  is a view showing a modification of the exposure apparatus shown in  FIG. 8  according to the third embodiment of the present invention;  
         [0105]      FIG. 10  is a view showing another exposure apparatus according to the third embodiment of the present invention;  
         [0106]      FIG. 11  is a view showing part of an exposure apparatus according to the fourth embodiment of the present invention including the periphery of a reticle;  
         [0107]      FIG. 12  is a flow chart of the overall manufacturing process of a semiconductor device;  
         [0108]      FIG. 13  is a flow chart of the overall manufacturing process of a semiconductor device;  
         [0109]      FIG. 14A  is a view showing part of a conventional exposure apparatus;  
         [0110]      FIG. 14B  is a view showing part of the conventional exposure apparatus;  
         [0111]      FIG. 15  is a view showing part of an exposure apparatus according to the fifth embodiment of the present invention;  
         [0112]      FIG. 16  is a view of the exposure apparatus of the fifth embodiment shown in  FIG. 15 , which is viewed from the lower side at the position of the opening plate;  
         [0113]      FIG. 17  is a view showing part of another exposure apparatus according to the fifth embodiment of the present invention;  
         [0114]      FIG. 18  is a view showing a modification of the exposure apparatus shown in  FIG. 16  according to the fifth embodiment of the present invention;  
         [0115]      FIG. 19  is a view showing another modification of the exposure apparatus shown in  FIG. 16  according to the fifth embodiment of the present invention;  
         [0116]      FIG. 20  is a view showing part of still another exposure apparatus according to the fifth embodiment of the present invention;  
         [0117]      FIG. 21  is a view of the exposure apparatus of the fifth embodiment shown in  FIG. 20 , which is viewed from the lower side at the position of the opening plate;  
         [0118]      FIG. 22  is a view showing part of still another exposure apparatus according to the fifth embodiment of the present invention;  
         [0119]      FIG. 23  is a view showing part of still another exposure apparatus according to the fifth embodiment of the present invention;  
         [0120]      FIG. 24  is a view showing part of still another exposure apparatus according to the fifth embodiment of the present invention;  
         [0121]      FIG. 25  is a view showing part of an exposure apparatus according to the sixth embodiment of the present invention;  
         [0122]      FIG. 26  is a view showing the sixth embodiment of the present invention from which the arrangement shown in  FIG. 1  is omitted;  
         [0123]      FIG. 27  is a view showing a modification of the exposure apparatus shown in  FIG. 2  according to the sixth embodiment of the present invention;  
         [0124]      FIG. 28  is a view showing another modification of the exposure apparatus shown in  FIG. 2  according to the sixth embodiment of the present invention;  
         [0125]      FIG. 29  is a view showing still another modification of the exposure apparatus shown in  FIG. 2  according to the sixth embodiment of the present invention;  
         [0126]      FIG. 30  is a view showing still another modification of the exposure apparatus shown in  FIG. 2  according to the sixth embodiment of the present invention;  
         [0127]      FIG. 31  is a view showing still another modification of the exposure apparatus shown in  FIG. 2  according to the sixth embodiment of the present invention;  
         [0128]      FIG. 32  is a view showing part of an exposure apparatus according to the seventh embodiment of the present invention; and  
         [0129]      FIG. 33  is a view showing an example in which a gas stream forming apparatus is installed in the space between the illumination optical system and the reticle in the sixth embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0130]     The preferred embodiments of the present invention will be described below with reference of the accompanying drawings.  
       First Embodiment  
       [0131]      FIG. 1  is a view showing part of an exposure apparatus according to the first embodiment of the present invention.  
         [0132]     This exposure apparatus has a light source such as an F 2  excimer laser (not shown) which generates a short-wavelength laser beam as illumination light. The illumination light (exposure light) from the light source uniformly illuminates a reticle (mask) through an appropriate illumination optical member. The light (exposure light) transmitted through the reticle reaches, through various optical members of a projecting optical system  101 , the surface of a wafer  103  placed on a wafer stage  102 , and forms a reticle pattern on the wafer surface.  
         [0133]     The wafer stage  102 , having the wafer  103  placed thereon, is designed to be movable in three-dimensional directions (X, Y, and Z directions). The reticle pattern is sequentially projected and transferred onto the wafer  103  by a so-called step-and-repeat scheme that repeats stepping movement and exposure. Even when the present invention is applied to a scanning exposure apparatus, the arrangement is almost the same as described above.  
         [0134]     For exposure, a heated and/or cooled inert gas (e.g., nitrogen gas, helium gas, or the like) is supplied from a supply port  113  through a supply valve  111  to a space (to be referred to as an optical path space hereinafter)  116  between the wafer  103  and a shielding member  115  on the lower side of the projecting optical system  101 , including the space through which the exposure light passes and the periphery of the space. The inert gas supplied to the periphery of the space. The inert gas supplied to the optical path space  116  is partially recovered from an exhaust port  114  and exhausted through an exhaust valve  112 . The supply valve  111 , supply port  113 , exhaust of a gas stream forming mechanism which forms a stream of a gas, such as an inert gas, in the optical path space  116 .  
         [0135]     Arrows in  FIG. 1  indicate the flow of the inert gas. To transmit alignment light, the shielding member  115  partially has a transparent member.  
         [0136]     Basically, the optical path space  116  is set at a positive pressure with respect to the ambient atmosphere (the pressure in the optical path space  116  is made higher than that in the ambient atmosphere), thereby decreasing the oxygen concentration in the exposure atmosphere in the optical path space. For this reason, the amount of inert gas that leaks from the optical path space  116  to the peripheral space is more than the exhaust amount through the exhaust valve  112 . The inert gas that has leaked from the optical path space  116  is recovered and exhausted by an exhaust unit  122  together with the ambient atmosphere supplied from a supply unit  121 .  
         [0137]     The inert gas that has leaked from the optical path space  116  is recovered and exhausted by the exhaust unit  122  together with the ambient atmosphere supplied as a heated and/or cooled gas (dry air or an inert gas having a low concentration) is supplied from the supply unit  121 . The temperature around the exposure region is adjusted by the ambient atmosphere.  
         [0138]     Opening/closing and the degrees of valve opening of the supply valve  111  and exhaust valve  112  are controlled by an environment controller  131 . Since the supply valve  111  and exhaust valve  112  are normally open, the inert gas is always supplied into the optical path space  116  independently of the position of the stage  102 . However, when the stage  102  is detached from the lower side of the optical path space  116  to do wafer exchange or maintenance, control may be performed to temporarily stop inert gas supply or reduce the supply amount. Supply may be started or the supply amount may be increased after wafer exchange or after the end of maintenance before the stage  102  moves to the lower side of the optical path space  116  again.  
         [0139]     The environment controller  131 , a stage controller  132 , and other controllers (not shown) are systematically controlled by a main controller  133  in various kinds of operations, including wafer exchange, alignment operation, and exposure operation. The control contents by the main controller  133  and the operation state of the exposure apparatus are monitored by a monitoring device  134 .  
         [0140]     If the atmosphere in the gap around the wafer  103  or at the step portion on the wafer stage  102  in the region that enters or leaves the optical path space  116  is insufficiently replaced, the ambient atmosphere may be involved in the optical path space when the wafer stage  102  moves. This may increase the oxygen concentration in the optical path space  116 .  
         [0141]     In the first embodiment, a member  151  is arranged to limit the height of the space around the optical path space  116  (especially, the space near the optical path space  116 ) and to form a predetermined space  150 . Let P 1  be the average concentration of the inert gas present in the optical path space  116 , and P 2  be the average concentration of the inert gas present outside the optical path space. The predetermined space  150  that surrounds the optical path space  116  is formed between the member  151  and the wafer  103  so that an average inert gas concentration P that satisfies: 
        P 2 &lt;P&lt;P 1  (a first condition) 
 
 is maintained. The concentration in the predetermined space  150  near the optical path space  116  is almost equal to the inert gas concentration in the optical path space  116 . Toward the outer periphery of the predetermined space  150 , the concentration becomes closer to that of the external atmosphere. In other words, the member  151  forms a gap space to the wafer  103 , thereby forming the space having the average inert gas concentration P. 
       
 
         [0143]     The distance H 1  from the lower surface (wafer-side surface) of the member  151  for forming the predetermined space  150  to the wafer is set to ½ or less, or more preferably, ⅓ or less of the width L 1  of the lower surface of the member  151  in a predetermined direction substantially parallel to the wafer (a second condition). (The distance may be distance to the wafer stage. An expression “the distance between the member  151  or another member and the wafer” in the following description is equivalent to “the distance between the member  151  or another member and the wafer stage.” Even for the reticle, the “reticle” can be replaced with the “reticle stage). Then, since the gas hardly flows in the predetermined space, the gas such as oxygen that absorbs exposure light is involved in the optical path space  116  at a low probability. The above “predetermined direction substantially parallel to the wafer” may be “the direction of a straight line at which the plane perpendicular to the wafer, including the direction of gas supply from the supply port  113 , and the plane including the wafer surface cross each other”, i.e., the “direction of gas stream in the optical path space” or the “scanning exposure direction of the wafer stage  102 ”.  
         [0144]     In addition, the height H 1  of the predetermined space  150  (the distance between the wafer and the lower surface of the member  151 ) is preferably less than the distance between the wafer and the optical element of the projecting optical system  101 , which is closest to the wafer (a third condition). Preferably, the height of the predetermined space is one-half, and more preferably, one-quarter the distance between the wafer and the optical element of the projecting optical system  101 , which is closest to the wafer. Accordingly, the place where the inert gas concentration becomes low can be separated from the optical path space  116 , so the inert gas concentration around the optical path space  116  can be stabilized at a high concentration.  
         [0145]     The predetermined space  150  may be formed in the optical path space  116  only on the upstream side of the gas stream in the optical path space  116  (on the supply port side in the optical path space  116 ). The predetermined space  150  may be formed on both the upstream and downstream sides of the gas stream in the optical path space  116 . The predetermined space  150  may be formed around the optical path space  116 .  
         [0146]     As a modification, a partitioning member  152  that forms the predetermined space  150  and also partitions the optical path space  116  may be designed, as shown in  FIG. 2 . The partitioning member  152  is arranged such that the distance between the wafer and the lower surface of the partitioning member  152  becomes shorter than that between the wafer and the optical element of the projecting optical system, which is closest to the wafer. As similar to the above second condition in the modification, when the ratio of the distance H 1  from the lower end of the member  152  that forms the predetermined space  150  to the wafer  103  to the width L 1  (the width in the direction substantially parallel to the wafer) of the member  152  that forms the predetermined space  150  is represented by 1:X, X is preferably 2 or more and, more preferably, 3 or more. If the X is less than 2, the inert gas concentration under the member  152  that forms the predetermined space  150  becomes considerably low, although it changes depending on the flow speed of the ambient atmosphere, the flow speed of the inert gas that leaks from the optical path space  116 , and the driving speed of the wafer stage  102 . When the height is limited, the inert gas that has leaked from the optical path space  116  hardly flows. With the collected inert gas, th influence of involvement when the wafer stage  102  moves is suppressed, and the atmosphere collected around the wafer  103  is replaced. Accordingly, the inert gas concentration in the purge space can be stabilized.  
         [0147]     Alternatively, as shown in  FIGS. 3 and 4 , an opening plate  158  that satisfies the above ratio may be arranged under the optical path space  116 .  FIG. 3  is a sectional view of an exposure apparatus in which the opening plate  158  is arranged under the optical path space  116  surrounded by a glass member  104  that passes alignment light and by the projecting optical system  101 , and the predetermined space  150  ( FIG. 2 ) is formed under the opening plate  158 .  FIG. 4  is a view of the opening plate  158  viewed from the lower side. In this embodiment, the exhaust port  114  is arranged, though it is not always necessary. A supply port may be formed in place of the exhaust port  114 .  
         [0148]     The inert gas is supplied from the supply port  113  into the optical path space  116 . At the same time, the inert gas may also be supplied to the predetermined space  150  by branching a pipe from the supply means for supplying the gas to the supply port or using another supply means. The predetermined space  150  to which the inert gas is supplied is preferably a predetermined space on the upstream side of the gas stream in the optical path space  116 .  
       Second Embodiment  
       [0149]     In the second embodiment, the member that forms a predetermined space  150  has, at its lower portion, partitioning member  153  that surround the periphery of an optical path space  116  multiple-fold (twofold together with a shielding member  115  in  FIG. 5 ) as shown in  FIG. 5 . When an inert gas that has leaked from the optical path space  116  is collected in a groove (a concave portion) formed by the partitioning members  153 , the atmosphere collected at the step and gap around a wafer  103  can be replaced. In addition, the influence of involvement by a wafer stage  102  or the influence of ambient atmosphere can be suppressed. Especially, in  FIG. 5 , the partitioning member  153  is arranged outside the optical path space  116  to surround the optical path space  116 . Referring to  FIG. 5 , the distance from the lower end of the partitioning member  153  to the wafer  103  is substantially equal to that from the lower end of the shielding member  115  to the wafer  103 . However, the distances may be different.  
         [0150]     As a modification,  FIG. 6  shown an arrangement having a plurality of partitioning members  153 . As the number of partitioning members  153  increases, the concentration of the collected inert gas can be increased toward the optical path space  166 . Hence, the atmosphere in the groove or at the step around the wafer  103  can be replaced at a more separated portion of the optical path space  116 . For this reason, the inert gas concentration in the optical path space  116  can be stabilized at a higher concentration.  
         [0151]     As another modification, when a member  154  having a plurality of grooves is arranged under the partitioning member  152  that forms the predetermined space  150  of the first embodiment shown in  FIG. 1 , as shown in  FIG. 7 , the same effect as described above can be obtained. The grooves are arranged to surround the optical path space  116  multiple-fold, like the partitioning member  152  or partitioning members  153  shown in  FIG. 5  or  6 . The depth of the groove is preferably equal to or less than the height from the final optical member under a projecting optical system  101  to the wafer  103 . If the groove is too deep, replacement in the groove requires time. Hence, a long time is required to replace the atmosphere collected in the gap or at the step around the wafer  103 .  
         [0152]     The distance between the partitioning member  153  and the shielding member  115  that shields the optical path space  116  from the ambient atmosphere in  FIG. 5 , the distance between the shielding member  115  and one of the partitioning members  153 , which is most closed to the optical axis of the projecting optical system  101 , in  FIG. 6 , or the width of the member  154  in a plane parallel to the page surface and including the optical axis of the projecting optical system (in other words, the above-described width in “a direction substantially parallel to the wafer”) in  FIG. 7  is preferably equal to or more than twice the distance between the wafer and one of the lower ends of the shielding member  115  and partitioning members  153 , which is closest to the wafer, in  FIG. 5  or  6 , or equal to or more than twice the distance between the wafer and the lower surface of the member  154  in  FIG. 7 . More preferably, the distance is not twice, but three times or more.  
         [0153]     The inert gas is supplied from the supply port  113  into the optical path space  116 . At the same time, the inert gas may also be supplied to one or a plurality of predetermined spaces  150  by branching a pipe from the supply means for supplying the gas to the supply port or using another supply means ( FIGS. 9 and 10  to be described later). The predetermined space  150 , to which the inert gas is supplied, is preferably a predetermined space  150  arranged on the upstream side of the gas stream in the optical path space  116 . For the exhaust side as well, the gas may be exhausted from the predetermined space  150  in a similar way. For the exhaust side, the gas is preferably exhausted from the predetermined space  150  arranged on the downstream side of the gas stream.  
       Third Embodiment  
       [0154]     In the third embodiment, the member  154 , supply port  113 , and exhaust port  114  of the second embodiment shown in  FIG. 7  are integrated to form a member  155  having a supply port  163  and an exhaust port  164  inside, as shown in  FIG. 8 . With this arrangement, the number of components can be reduced. As for the depths of the grooves formed in the member  155 , the groove around an optical path space  116  is shallowest, i.e., the grooves become shallow inside the member  155  centered on the optical path space  116  and deep outside.  
         [0155]     The inner grooves of the member  155  are made shallow to shorten the replacement time at the inner part and maintain a high concentration at the inner part. The outer grooves of the member  155  are made deep to increase the volume and to suppress a decrease in inert gas concentration due to entrance of ambient atmosphere because the outer part is readily influenced by the ambient atmosphere, and the internal inert gas concentration abruptly decreases due to a transient change if the volume is small. Transient phenomena include abrupt reverse driving of a wafer stage  102  or entrance of a step or groove around the wafer  103  into the optical path space  116 .  
         [0156]     In  FIG. 8 , the grooves formed in the member  155  become shallow toward the optical path space  116 . Instead of changing the depth, even when the width of the groove is increased outward from the optical path space  116 , the same effect as described above can be obtained.  
         [0157]     As a modification, when a member  156  having openings  157  that extend from the supply port  163  and exhaust port  164  in the member  155  shown in  FIG. 8  to the multiple grooves is arranged, as shown in  FIG. 9 , the atmosphere in the grooves can be effectively replaced. In this case, the openings  157  to the grooves must be much smaller than the openings of the supply port  163  and exhaust port  164 . When the openings  157  are large, the atmosphere in the grooves enters the supply port  163  and exhaust port  164  to decrease the inert gas concentration in the optical path space  116 . In addition, the openings  157  corresponding to the grooves preferably become outwardly smaller.  
         [0158]     To decrease the number of components, the member that forms the predetermined space  150 , the supply port, and the exhaust port may be integrated even as shown in  FIG. 1  or  2  of the first embodiment or  FIG. 5  of the second embodiment.  
         [0159]     As another modification, to increase the exhaust efficiency in the optical path space  116 , as shown in  FIG. 10 , a shielding member  125  is formed by forming openings  126  in the shielding member  115  that forms the optical path space  116  in the arrangement of the second embodiment shown in  FIG. 6  such that the inert gas that has leaked from the openings  126  can blow in the partitioning members  153 , like the inert gas that has leaked from the lower side of the optical path space  116 .  
         [0160]     In this case, when the openings  126  are formed at portions where the flow speed in the optical path space  116  decreases, the exhaust efficiency in the optical path space  116  can be increased. Accordingly, the replacement time in the optical path space  116  can be shortened. The distance from the lower end of the partitioning members  153  to the wafer  103  is preferably larger than the distance from the lower end of the shielding member  125  to the wafer  103 .  
         [0161]     In the above embodiments, the optical path space  116  has an exhaust port. When recovery of ambient atmosphere is taken into consideration, the exhaust port may be used as another supply port. When the exhaust port is used as a supply port, the influence of ambient atmosphere can be further suppressed even when the consumption amount is kept unchanged.  
       Fourth Embodiment  
       [0162]     The present invention applied to the space between the projection optical system and the wafer stage in the first to third embodiments can also be applied to the space between an illumination optical system and a reticle stage and the space between the reticle stage and the projecting optical system.  FIG. 11  is a view showing an exposure apparatus in which the present invention is applied to the space between the projecting optical system and the wafer stage, the space between the illumination optical system and the reticle stage, and the space between the reticle stage and the projecting optical system.  
         [0163]     In the exposure apparatus shown in  FIG. 11 , for a first optical path space  314  between a final optical member (cover glass)  311  of a projecting optical system  302  and a wafer chuck  303  (wafer  305 ), a first supply unit  341 , which supplies an inert gas to the first optical path space  314  through a supply valve  312 , and a first exhaust unit  342 , which exhausts the inert gas, and the like, from the first optical path space  314  through an exhaust valve  313  are arranged. A member  501 , which forms a first predetermined space  401  for limiting the height around the first optical path space  314 , is arranged. With this arrangement, a portion where the inert gas concentration decreases can be separated from the first optical path space  314 , and the inert gas concentration around the first optical path space  314  can be stabilized at a high concentration.  
         [0164]     For a second optical path space  326  between an illumination optical system  301 , which illuminates a reticle (mask)  322  and a reticle stage (reticle  322 )  321 , a second supply unit  351 , which supplies an inert gas to the second optical path space  326  through a supply valve  327 , and a second exhaust unit  352 , which exhausts the inert gas, and the like, from the second optical path space  326  through an exhaust valve  328  are arranged. A member  502 , which forms a second predetermined space  402  for limiting the height around the second optical path space  326 , is arranged. With this arrangement, a portion where the inert gas concentration decreases can be separated from the second optical path space  326 , and the inert gas concentration around the second optical path space  326  can be stabilized at a high concentration.  
         [0165]     For a third optical path space  325  between the reticle stage  321  and the projecting optical system  302 , a third supply unit  345 , which supplies an inert gas to the third optical path space  325  through a supply valve  323 , and a third exhaust unit  346 , which exhausts the inert gas, and the like, from the third optical path space  325  through an exhaust valve  324 , are arranged. A member  503 , which forms a third predetermined space  403  for limiting the height around the third optical space  325 , is arranged. With this arrangement, a portion where the inert gas concentration decreases can be separated from the third optical path space  325 , and the inert gas concentration around the third optical path space  325  can be stabilized at a high concentration.  
         [0166]     In this way, the inert gas concentration around the first to third optical path spaces  314 ,  326 , and  325  can be stabilized at a high concentration.  
         [0167]     As in the first embodiment, in the exposure apparatus shown in  FIG. 11 , opening/closing and the degrees of valve opening of the supply and exhaust valves are controlled by an environment controller (not shown). The reticle stage  321  is controlled by a stage controller (not shown) in synchronism with a wafer stage  304 . The environment controller, stage controller, and other controllers (not shown) are systematically controlled by a main controller (not shown) in various kinds of operations including wafer exchange, alignment operation, and exposure operation. The control contents by the main controller and the operation state of the exposure apparatus are monitored by a monitoring device (not shown).  
         [0168]     The form of formation of the predetermined space for maintaining the average concentration P of the inert gas may be replaced with that described in the second or third embodiment.  
       Fifth Embodiment  
       [0169]      FIG. 15  is a view showing part of an exposure apparatus according to the fifth embodiment of the present invention.  
         [0170]     An inert gas is supplied from a supply port  113  through a supply valve  111  into an optical path space  116 . The inert gas supplied into the optical path space  116  is partially recovered from an exhaust port  14  through an exhaust valve  112 .  
         [0171]     When the inert gas is supplied from one direction, the amount of inert gas that leaks from the optical path space  116  to a predetermined space  150  is larger in the +X direction (exhaust port side). If the distance from an opening plate  157  to the surface of a wafer  103  is long, the leakage amount difference becomes conspicuous. A supply port, which injects the inert gas from the lower surface of the wafer  103 , is added.  FIG. 16  is a view of the opening plate  157  in  FIG. 15 , which is viewed from the lower side (−Y direction). When slit-like openings are added to the supply port  113  and opening plate  157 , the inert gas concentration in the predetermined space  150  on the lower side of the supply port  113  can be stabilized at a high concentration.  
         [0172]     As a modification, supply of the inert gas to the optical path space  116  and supply of the inert gas to the predetermined space  150  may be separated, and the supply amounts may be controlled by separate mass flow controllers MFC 1  and MFC 2 , as shown in  FIG. 17 . In  FIG. 15 , when the inert gas is supplied from the opening into the predetermined space  150 , the atmosphere around the stage is involved at the time of stage movement. The inert gas concentration near the opening decreases, and even the inert gas concentration in the supply port  113  may sometimes decrease. However, when the supply systems are separated, as shown in  FIG. 17 , the concentration of the inert gas supplied from the supply port  113  can be stabilized at a high concentration.  
         [0173]     In  FIG. 16 , a slit-like opening is formed. As a modification, when an arc opening is arranged to surround the optical path space  116 , as shown in  FIG. 18 , the influence of the atmosphere around the optical path space  116  can be further suppressed.  
         [0174]     As still another modification, as shown in  FIG. 19 , a groove may be formed on the predetermined space  150  side of the place where the opening plate  157  shown in  FIG. 16  has openings, and a plurality of openings (five openings in  FIG. 19 ) may be formed in the groove to inject the inert gas from the opening plate  157  to the wafer surface side. When the distance from the opening plate  157  to the surface of the wafer  103  is as short as 2 mm or less, the groove is filled with the inert gas. Hence, the inert gas concentration in the predetermined space  150  on the lower side of the supply port  113  can be stabilized at a high concentration. The size of the opening shown in  FIG. 19  can be minimized as compared to the size of the opening shown in  FIG. 16 . For this reason, even when the ambient atmosphere is involved, the decrease in inert gas to the supply source can be suppressed.  
         [0175]     In  FIGS. 18 and 19  as well, the inert gas may be commonly supplied to the optical path space  116  and predetermined space  150 , as shown in  FIG. 15 . Alternatively, as shown in  FIG. 17 , supply of the inert gas to the predetermined space  150  may be separated. When the supply amounts are controlled by the separate mass flow controllers MFC 1  and MFC 2 , the concentration of the inert gas supplied from the supply port  113  can be stabilized at a high concentration.  
         [0176]      FIGS. 20 and 21  show still another modification. In this modification, a groove that surrounds the optical path space  116  is formed in the opening plate  157  of the embodiment shown in  FIG. 15  or  16 . When the distance from the opening plate  157  to the surface of the wafer  103  is as short as 2 mm or less, the groove is filled with the inert gas. Hence, the inert gas concentration around the optical path space  116  can be stabilized at a high concentration. Alternatively, as shown in  FIG. 22 , when an opening from which the inert gas is injected may be added to the lower portion of the exhaust port  114  in the embodiment shown in  FIG. 17 . In this case, even when the ambient atmosphere is involved from the exhaust port side, the decrease in inert gas concentration can be suppressed. Referring to  FIG. 22 , the supply amounts can be different mass flow controllers MFC 1 , MFC 2 , and MFC 3 . Hence, the flow rates can be optimized in accordance with the arrangement.  
         [0177]     As shown in  FIG. 23 , a groove that surrounds the optical path space  116  may be formed in the opening plate  157 , and a plurality of openings (10 openings in  FIG. 23 ) may be formed in the groove to inject the inert gas from the opening plate  157  to the wafer surface side. Alternatively, as shown in  FIG. 24 , grooves that partially surround the optical path space  116  may be formed, and a plurality of openings (10 openings in  FIG. 24 ) may be formed in the groove to inject the inert gas from the opening plate  157  to the wafer surface side.  
         [0178]     In  FIGS. 23 and 24  as well, the inert gas may be commonly supplied to the optical path space  116  and predetermined space  150 , as shown in  FIG. 15 . Alternatively, as shown in  FIG. 22 , supply of the inert gas to the optical path space  116  and supply of the inert gas to the predetermined space  150  may be separated. When the supply amounts are controlled by the separate mass flow controllers MFC 1 , MFC 2 , and MFC 3 , the concentration of the inert gas supplied from the supply port  113  can be stabilized at a high concentration.  
         [0179]     The above embodiments assume that the supply amount of the inert gas to the optical path space  116  is set to be equal to or more than the exhaust amount. If the optical path space is not set to a positive pressure, the optical path space draws the ambient atmosphere. Hence, the inert gas concentration in the optical path space decreases, and the exposure light transmittance decreases. However, in the arrangements shown in  FIGS. 23 and 24 , inert gas supply to the optical path space  116  is separated from inert gas supply to the predetermined space  150 , and the supply amounts are controlled by the separate mass flow controllers MFC 1 , MFC 2 , and MFC 3 . In this case, even when the pressure in the optical path space  116  is lower than that in the predetermined space  150 , the inert gas concentration in the optical path space can be stabilized at a high concentration by setting the inert gas supply amount to the predetermined space  150  to be larger. For this reason, the exhaust amount can be increased, and contamination generated from the wafer surface at the time of exposure can be efficiently exhausted.  
         [0180]     The opening plate  157  need not be independently prepared. Instead, an opening portion may be formed in the supply means or exhaust means.  
         [0181]     The distance between the opening plate  157  (lower surface (wafer-side surface) of the supply means or exhaust means) and the wafer is set to one-half or less, or more preferably, one-third or less of the width corresponding to the distance between the outer periphery of the optical path space  116  and that of the opening plate  157  in a predetermined direction substantially parallel to the wafer. In this case, since the gas hardly flows in the predetermined space, the gas, such as oxygen, that absorbs exposure light is involved in the optical path space  116  at a low probability.  
         [0182]     In addition, the height of the predetermined space  150  (the distance between the wafer and the lower surface of the opening plate  157 ) is preferably less than the distance between the wafer and the optical element of a projecting optical system  101 , which is closest to the wafer. Preferably, the height of the predetermined space  150  is one-half or less, and more preferably, one-quarter or less the distance between the wafer and the optical element of the projecting optical system  101 , which is closest to the wafer. Accordingly, the place where the inert gas concentration becomes low can be separated from the optical path space  116 , so the inert gas concentration around the optical path space  116  can be stabilized at a high concentration.  
         [0183]     The predetermined space  150  may be formed in the optical path space  116  only on the upstream side of the gas stream in the optical path space  116  (on the supply port side in the optical path space  116 ). The predetermined space  150  may be formed on both the upstream and downstream sides of the gas stream in the optical path space  116 . The predetermined space  150  may be formed around the optical path space  116 .  
         [0184]     In the above first to fifth embodiments, an exposure apparatus is arranged to satisfy the first to third conditions, so that the effects of each of the first to fifth embodiments will be more remarkable.  
       Sixth Embodiment  
       [0185]      FIGS. 25 and 26  are views showing part of an exposure apparatus according to the sixth embodiment of the present invention. This exposure apparatus has a light source such as an F 2  excimer laser (not shown) which generates a short-wavelength laser beam as illumination light. The illumination light (exposure light) from the light source uniformly illuminates a reticle (mask) through an appropriate illumination optical member. The light (exposure light) transmitted through the reticle reaches, through various optical members of a projecting optical system, the surface of a wafer placed on a wafer stage installed in a chamber having a supply unit and an exhaust unit, and forms a reticle pattern on the wafer surface.  
         [0186]     The wafer stage having the wafer placed thereon is designed to be movable in three-dimensional directions (X, Y, and Z directions). The reticle pattern is sequentially projected and transferred onto the wafer by a so-called step-and-repeat scheme that repeats stepping movement and exposure. Even when the present invention is applied to a scanning exposure apparatus, the arrangement is almost the same as described above.  
         [0187]     For exposure, an inert gas (e.g., nitrogen gas, helium gas, or the like), whose temperature and impurity concentration are accurately managed, is supplied from a supply port through a supply valve to a local space, including the space through which the exposure light passes in the gas stream forming apparatus on the lower side of the projecting optical system and the periphery of the space. The inert gas supplied to the local space is partially recovered from an exhaust port and exhausted through an exhaust valve. Arrows in  FIG. 25  indicate the flow of the inert gas.  
         [0188]     Basically, the local space is set at a positive pressure with respect to the ambient atmosphere (the pressure in the local space is made higher than that in the ambient atmosphere), thereby decreasing the oxygen concentration in the exposure atmosphere in the local space. For this reason, the amount of inert gas that leaks from the local space to the peripheral space is more than the exhaust amount through the exhaust valve. The inert gas that has leaked from the local space is recovered and exhausted by an exhaust unit together with the chamber atmosphere supplied from a supply unit. The temperature and impurity concentration of the chamber atmosphere in the local space containing the exposure atmosphere are accurately managed by the gas stream forming apparatus. Hence, the gas supplied from the supply unit can be a gas whose temperature and impurity concentration are managed moderately as much as possible.  
         [0189]     Opening/closing and the degrees of valve opening of the supply valve and exhaust valve are controlled by an environment controller. Since the supply valve and exhaust valve are normally open, the inert gas is always supplied into the local space independently of the position of the stage. However, when the stage is detached from the lower side of the local space to do wafer exchange or maintenance, control may be performed to temporarily stop inert gas supply or reduce the supply amount. Supply may be started or the supply amount may be increased after wafer exchange before the stage moves to the lower side of the local space again.  
         [0190]     The environment controller, a stage controller, and other controllers (not shown) are systematically controlled by a main controller in various kinds of operations including wafer exchange, alignment operation, and exposure operation. The control contents by the main controller and the operation state of the exposure apparatus are monitored by a monitoring device.  
         [0191]     If the atmosphere in the gap around the wafer  103  or at the step portion on the wafer stage in the region that enters or leaves the local space is insufficiently replaced, the ambient atmosphere may be involved in the optical path space when the wafer stage moves. This may increase the oxygen concentration in the local space.  
         [0192]     In the sixth embodiment, to maintain the oxygen concentration in the local space to the set value or less, the gas stream forming apparatus is installed on the projecting optical system side while separated from the wafer by a narrow space. A distance H 1  of the narrow space between the gas stream forming apparatus and the wafer is preferably equal to or less than ½, or more preferably, ⅕ of a distance H 0  of the local space between the projecting optical system and the wafer. Accordingly, the oxygen concentration in the local space can be maintained to the set value or less. A length L 1  of the narrow space along the gas stream is preferably set to twice or more, and preferably three times more, of the distance H 1 .  
         [0193]     For the outer shape of the gas stream forming apparatus, the section of the gas stream forming apparatus shown in  FIG. 25  may be extended in the depth direction of the purge surface. The gas stream forming apparatus may alternatively have a rotationally symmetrical shape with respect to the exposure optical axis. The outer shape is not particularly limited to the above shapes.  
         [0194]     In the local space, for example, an inorganic gas may be generated from the resist applied to the wafer. The organic gas may react with exposure light and contaminate the surface of the lens of the projecting optical system. This may fog the lens and decrease the exposure light intensity.  
         [0195]     To prevent this, in the sixth embodiment, a restricting member, which partially reduces the sectional area of the local space in a direction from the projecting optical system to the wafer, is arranged at the outlet of the supply port in the local space. The narrow space suppresses any vortex flow generated when the gas in the local space moves from the wafer side to the projecting optical system side along an axis corresponding to the vertical direction of the page surface. Hence, the organic gas or the like generated from the resist applied to the wafer is quickly exhausted. Since the concentration of the organic gas reaching the lens of th projecting optical system can be sufficiently reduced, fogging on the lens can be suppressed. In addition, since the inert gas in the local space smoothly flows, the oxygen concentration in the local space can be more quickly reduced.  
         [0196]     The installation position of the restricting member is not limited to the supply side of the local space, as shown in  FIG. 26 . The restricting member may be arranged on the exhaust side, as shown in  FIG. 27 , or on both the supply and exhaust sides, as shown in  FIG. 28 .  
         [0197]     As a modification, the exhaust mechanism in  FIG. 27  may be changed to a supply mechanism having opposing supply ports in the local space, and a restricting member may be arranged at each supply port, as shown in  FIG. 29 . In this case, the inert gas supply amounts from the supply ports, and the lengths and positions of the restricting members need not always be symmetrical. An asymmetrical arrangement (the restricting members have different heights in the optical axis direction of the projecting optical system) shown in  FIG. 30  can more effectively prevent contamination.  
         [0198]     As another modification, instead of arranging a restricting member, a notch portion removing the wafer-side part of the gas stream forming apparatus near the supply port is installed to partially widen the narrow space, as shown in  FIG. 31 . With this arrangement, the same effect as that obtained by arranging the restricting member can be expected.  
         [0199]     In this embodiment, the restricting member is fixed. However, a driving mechanism for moving the restricting member may be added to move the restricting member in accordance with the exposure state. In this case, for example, when the stage should be moved without performing exposure, the projecting amount of the restricting member can be increased to prevent any decrease in inert gas concentration. During exposure, the restricting member can be retracted so as not to shield the exposure light.  
         [0200]     In this embodiment, the projecting optical system, wafer, and the wafer stage have been described in detail. The present invention can also be applied to the illumination optical system, reticle, and reticle stage, as shown in  FIG. 33 .  
       Seventh Embodiment  
       [0201]     In the seventh embodiment, two supply/exhaust systems are prepared in the gas stream forming apparatus, as shown in  FIG. 32 . Two supply ports oppose each other on the projecting optical system side. A supply port and an exhaust port oppose each other on the wafer side. A restricting member is arranged between the two pairs of supply ports/exhaust ports.  
         [0202]     According to this arrangement, the two opposing supply ports and exhaust ports on the projecting optical system side suppress an impurity gas which is generated from the resist applied to the wafer and reaches the projecting optical system. Hence, the impurity gas can be quickly exhausted by the gas stream formed by the supply port and exhaust port on the wafer side.  
         [0203]     Each of the supply/exhaust system on the projecting optical system side and that on the wafer side may have both the supply port and exhaust port.  
         [0204]     In the above sixth and seventh embodiments, an exposure apparatus is arranged to satisfy the first to third conditions, so that the effects of each of the first to fifth embodiments will be more remarkable.  
         [0205]     [Application Example of Exposure Apparatus] 
         [0206]     A semiconductor device manufacturing process using the above exposure apparatus will be described next.  
         [0207]      FIG. 11  shows the flow of the overall manufacturing process of a semiconductor device.  
         [0208]     In step  1  (circuit design), the circuit of a semiconductor device is designed. In step  2  (mask preparation), a mask is prepared on the basis of the designed circuit pattern. In step  3  (wafer manufacture), a wafer is manufactured using a material such as silicon. In step  4  (wafer process), called a preprocess, an actual circuit is formed on the wafer by lithography using the mask and wafer.  
         [0209]     In step  5  (assembly), called a post-process, a semiconductor chip is formed from the wafer prepared in step  4 . This step includes processes such as assembly (dicing and bonding) and packaging (chip encapsulation). In step  6  (inspection), inspections including an operation check test and a durability test of the semiconductor device manufactured in step  5  are performed. A semiconductor device is completed with these processes and shipped in step  7 .  
         [0210]      FIG. 13  shows details of the wafer process.  
         [0211]     In step  11  (oxidation), the surface of the wafer is oxidized. In step  12  (CVD), an insulating film is formed on the wafer surface. In step  13  (electrode formation), an electrode is formed on the wafer by deposition. In step  14  (ion implantation), ions are implanted into the wafer. In step  15  (resist process), a photosensitive agent is applied to the wafer. In step  16  (exposure), the circuit pattern is transferred to the wafer using the above exposure apparatus. In step  17  (development), the exposed wafer is developed. In step  18  (etching), portions other than the developed resist image are etched. In step  19  (resist removal), any unnecessary resist remaining after etching is removed. By repeating these steps, a multilayered structure of circuit patterns is formed on the wafer.  
         [0212]     As many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof, except as defined in the appended claims.