Abstract:
An exposure apparatus includes a movable stage, a chuck device which is arranged on the stage and holds a substrate, a first gas supply device for supplying a gas to a position of the substrate to be exposed, and a plurality of divided planar members which are arranged adjacent to a periphery of the substrate such that at least a part of the divided planar members covers a position measurement mirror of the movable stage, and are flush with or substantially flush with a surface of the substrate or a substrate holding surface of the chuck device.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an exposure apparatus used in a semiconductor manufacturing process, particularly, to a projection exposure apparatus which projects and transfers a reticle pattern onto a silicon wafer and, more particularly, to an exposure apparatus using a reticle stage and a wafer stage, which sequentially move a reticle and a silicon wafer with respect to a projection exposure system when projecting a reticle pattern onto the wafer. 
     BACKGROUND OF THE INVENTION 
     A conventional semiconductor manufacturing process uses a projection exposure apparatus which projects and transfers a reticle pattern onto a silicon wafer. 
     A conventional projection exposure apparatus is shown in FIGS. 16 to  20 . 
     In FIGS. 16 to  20 , reference numeral  101  denotes an illumination system unit having an exposure light source and a function of shaping exposure light and irradiating a reticle with the shaped light;  102 , a reticle stage which supports a reticle serving as an exposure pattern master and performs a reticle scan operation with respect to a wafer at a predetermined reduction exposure magnification ratio;  103 , a reduction projection lens which reduces a master pattern and projects it onto a wafer (substrate);  104 , a wafer stage which sequentially, continuously moves a substrate (wafer) for every exposure; and  105 , an exposure apparatus main body which supports the reticle stage  102 , reduction projection lens  103 , and wafer stage  104 . 
     Reference numerals  106  and  107  denote a wafer stage purge partition and a reticle stage space purge partition for purging the wafer and reticle stage spaces with helium or nitrogen. The purposes of these partitions are to prevent, in general air, ozone generated by absorbing, in oxygen in air, F 2  laser (λ=157 nm), which is vacuum ultraviolet radiation (VUV) serving as exposure light, to prevent silicon oxide generated by absorption in silicon in air, and to prevent a decrease in the transmittance of exposure light caused by ammonia or silanol, which is generated by hydrolysis of organic gas such as siloxane or silazane and moisture in the air, and attaches to lens glass. 
     In other words, the wafer stage space is closed for efficient purge with helium or nitrogen supplied to increase the transmittance of exposure light. The oxygen and moisture concentrations in the space are decreased to 100 to 1,000 ppm. 
     Reference numeral  108  denotes a wafer purge nozzle, which is arranged to locally purge an exposure portion on the upper surface of a wafer with high-purity nitrogen gas and decreases oxygen and moisture concentrations to 10 ppm or less, which is lower than the oxygen concentrations (100 to 1,000 ppm) within the wafer stage purge partition  106  and reticle stage purge partition  107 . 
     A wafer stage purge pipe  109 , reticle stage purge pipe  110 , and wafer purge pipe  111  are used to supply purge gas (helium, nitrogen, or the like) from a purge gas supply unit  112 , to interiors of the partitions and the purge nozzle. 
     In FIG. 17, reference numeral  115  denotes a wafer whose single-crystal silicon substrate surface is coated with a resist in order to project and to transfer a reticle pattern drawn on a reticle substrate via a reduction exposure system;  113 , a fine moving stage, which finely adjusts the wafer  115  in the optical axis direction and tilt direction of the reduction exposure system and a rotational direction of the reduction exposure system and a rotational direction about the optical axis as a center;  114 , a wafer chuck, which supports and fixes the wafer  115  onto the fine moving stage  113 ;  116 , an X bar mirror, which is a target for measuring the X position of the fine moving stage  113  by a laser interferometer;  117 , a Y bar mirror, which is a target for measuring the Y position of the fine moving stage  113 , and  118 , an illuminance sensor, which is arranged on the upper surface of the fine moving stage  113 , calibrates and measures the illuminance of exposure light before exposure, and uses the illuminance for correction of the exposure amount. 
     Reference numeral  119  denotes a stage reference mark, which is arranged on the upper surface of the fine moving stage  113  and has a stage alignment measurement target;  120 , an X linear motor, which moves and drives the fine moving stage  113  in the X direction;  121 , an X guide, which moves and guides the fine moving stage  113  in the X direction;  122 , a Y guide, which moves and guides the X guide  121  and fine moving stage  113  in the Y direction;  123  and  124 , Y linear motors, which move and drive the fine moving stage  113  in the Y direction; and  125 , a stage surface plate, which plane-guides the fine moving stage  113 . 
     As shown in FIGS. 18A and 18B, slit exposure light  126  is emitted to the center of the optical path of the exposure light. The wafer purge nozzle  108  is set above the exposed portion, and the space above the wafer  115  is purged with purge gas (nitrogen or the like) injected from the wafer purge nozzle  108 . An oxygen concentration of 10 ppm is achieved around the center of the wafer  115 . As shown in FIGS. 19A,  19 B,  20 A, and  20 B, a gap of up to about 1 mm is formed between the wafer purge nozzle  108  and the wafer  115  in the direction of height, and a gap of up to about 2 mm is formed between the wafer purge nozzle  108  and the wafer chuck  114  when a shot near the periphery of the wafer  115  is to be exposed with the slit exposure light  126 . The conventional wafer chuck  114  does not have a peripheral member which shields the wafer chuck  114  from a purge gas flow from the wafer purge nozzle  108 . In exposing the wafer periphery, purge gas from the wafer purge nozzle  108  leaks in a large amount from the periphery of the wafer chuck  114  to decrease the pressure of the purge space. Gas other than purge gas externally flows into the purge space to increase the oxygen concentration to about 100 to 1,000 ppm. A low oxygen concentration equal to or less than a specified value (10 ppm or less) cannot be maintained. 
     SUMMARY OF THE INVENTION 
     The present invention has been made to overcome the conventional drawbacks, and has as its object to prevent a decrease in purge pressure in exposure and an increase in oxygen concentration caused by a purge error near the periphery of a wafer or a reticle. 
     To overcome the conventional drawbacks and to achieve the same object, an exposure apparatus according to the first aspect of the present invention has the following arrangement. 
     That is, the exposure apparatus comprises a movable stage, a chuck device, which is arranged on the stage and holds a substrate, a gas supply device for supplying gas to a position of the substrate to be exposed, and a planar member, which is arranged adjacent to a periphery of the substrate, is flush with or substantially flush with a surface of the substrate, and is integrated with the chuck device. 
     A device manufacturing method according to the present invention has the following steps. 
     That is, the device manufacturing method comprises the steps of applying a photosensitive material to a substrate, transferring a pattern to the photosensitive material applied to the substrate by the above-described exposure apparatus, and developing the substrate bearing the pattern. 
     Other objects and advantages besides those discussed above shall be apparent to those skilled in the art from the description of a preferred embodiment of the invention which follows. In the description, reference is made to the accompanying drawings, which form a part hereof, and which illustrate an example of the invention. Such an example, however, is not exhaustive of the various embodiments of the invention, and, therefore, reference is made to the claims which follow the description for determining the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view showing the whole arrangement of an exposure apparatus according to the first embodiment of the present invention; 
     FIG. 2 is a perspective view showing a stage device in FIG. 1; 
     FIG. 3 is an enlarged, perspective view showing a fine moving stage and a purge plate; 
     FIGS. 4A and 4B are a plan view and a side view showing the purge plate; 
     FIGS. 5A and 5B show plan views and side vies of a purge device; 
     FIGS. 6A and 6B are plan views showing the purge plate; 
     FIG. 7 is a perspective view showing a stage device according to the second embodiment of the present invention; 
     FIG. 8 is an enlarged, perspective view showing a fine moving stage and a purge plate according to the second embodiment; 
     FIG. 9 is a plan view for explaining a chuck exchange method according to the second embodiment; 
     FIG. 10 is an enlarged, perspective view showing a fine moving stage and a purge plate according to the third embodiment; 
     FIG. 11 is an enlarged, perspective view showing the fine moving stage and purge plate according to the third embodiment; 
     FIG. 12 is an enlarged, perspective view showing the fine moving stage and purge plate according to the third embodiment; 
     FIG. 13 is a perspective view showing a fine moving stage and purge plate according to the fourth embodiment; 
     FIG. 14 is an enlarged, perspective view showing the fine moving stage and purge plate according to the fourth embodiment; 
     FIGS. 15A and 15B are a plan view and a side view showing the purge plate according to the fourth embodiment; 
     FIG. 16 is a view showing the whole arrangement of a conventional exposure apparatus; 
     FIG. 17 is a perspective view showing the whole arrangement of a conventional stage device; 
     FIGS. 18A and 18B are a plan view and a side view showing a conventional purge plate; 
     FIGS. 19A and 19B show plan views and side views of a conventional purge device; 
     FIGS. 20A and 20B are plan views showing the conventional purge plate; 
     FIG. 21 is a flow chart showing the overall manufacturing process of a semiconductor device; 
     FIG. 22 is a flow chart showing a detailed wafer process in FIG. 21; 
     FIG. 23 is a perspective view showing the stage device of an exposure apparatus according to the fifth embodiment of the present invention; 
     FIG. 24 is an enlarged, perspective view showing a fine moving stage and a purge plate; 
     FIGS. 25A and 25B are a plan view and a side view showing the purge plate; 
     FIGS. 26A and 26B show plan views and side views of a purge device; 
     FIGS. 27A and 27B are plan views showing the purge device; 
     FIG. 28 is a view for explaining a chuck exchange method; and 
     FIGS. 29A and 29B are a plan view and a side view showing the sixth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. 
     (First Embodiment) 
     FIGS. 1 to  6 B are views showing the arrangement of an exposure apparatus according to the first embodiment of the present invention. 
     The following description will use a “substrate”, which means a wafer or a reticle. 
     In FIGS. 1 to  6 B, reference numeral  1  denotes an illumination system unit having an exposure light source and a function of shaping exposure light and irradiating a reticle (substrate) with the shaped light;  2 , a reticle stage, which supports a reticle serving as an exposure pattern master and performs a reticle scan operation with respect to a wafer;  3 , a reduction projection lens, which reduces a master pattern and projects it onto a wafer (substrate);  4 , a wafer stage, which sequentially, continuously moves a substrate (wafer) for every exposure; and  5 , an exposure apparatus main body, which supports the reticle stage  2 , projection lens  3 , and wafer stage  4 . 
     Reference numerals  6  and  7  denote a wafer stage purge partition and a reticle stage space purge partition for purging spaces around the wafer stage  4  and reticle stage  2  with helium or nitrogen. 
     The purposes of these partitions are to prevent, in general air, ozone generated by absorbing, in oxygen in air, F 2  laser (λ=157 nm), which is vacuum ultraviolet radiation (VUV) serving as exposure light, to prevent silicon oxide generated by absorption in a silicon-based impurity in air, and to prevent a decrease in the transmittance of exposure light caused by ammonia or silanol, which is generated by hydrolysis of moisture in air and organic gas such as siloxane or silazane volatilized from various acids, solvents, and the like, and attaches to lens glass. 
     In other words, the wafer stage purge partition  6  and a reticle stage space purge partition  7  are arranged to close the wafer stage space for efficient purge with helium or nitrogen serving as purge gas supplied to increase the transmittance of exposure light. The oxygen and moisture concentrations in the space are decreased to 100 to 1,000 ppm. 
     Reference numeral  8  denotes a wafer purge nozzle, which is arranged to locally purge an exposure portion on the upper surface of a wafer with high-purity nitrogen gas and decreases oxygen and moisture concentrations to 10 ppm or less, which is lower than the oxygen concentrations (100 to 1,000 ppm) within the wafer stage purge partition  6  and reticle stage purge partition  7 . 
     A wafer stage purge pipe  9 , a reticle stage purge pipe  10 , and a wafer purge pipe  11  are used to supply purge gas (e.g., helium, nitrogen, or the like) from a purge gas supply unit  12  to the interiors of the partitions and the purge nozzle. 
     In FIG. 2, reference numeral  15  denotes a wafer whose single-crystal silicon substrate surface is coated with a resist in order to project and to transfer a reticle pattern drawn on a reticle substrate via a reduction exposure system;  13 , a fine moving stage, which finely adjusts the wafer  15  in the optical axis direction and tilt direction of the reduction exposure system and a rotational direction about the optical axis as a center;  14 , a wafer chuck, which supports and fixes the wafer  15  onto the fine moving stage  13 ;  16 , an X bar mirror, which is a target mirror for measuring the X position of the fine moving stage by a laser interferometer (not shown); and  17 , a Y bar mirror, which is a target for measuring the Y position of the fine moving stage. 
     Reference numeral  18  denotes an illumination sensor, which is arranged on the upper surface of the fine moving stage  13 , calibrates and measures the illuminance of exposure light before exposure, and uses the illuminance for correction of the exposure amount. 
     Reference numeral  19  denotes a stage reference mark, which is arranged on the upper surface of the fine moving stage  13  and has a stage alignment measurement target. Alignment of the master and wafer stage, and the like, are performed by an alignment measurement device (not shown). 
     Reference numeral  20  denotes an X linear motor, which moves and drives the fine moving stage  13  in the X direction;  21 , an X guide, which moves and guides the fine moving stage  13  in the X direction;  22 , a Y guide, which moves and guides the X guide  21  and fine moving stage  13  in the Y direction;  23  and  24 , Y linear motors, which move and drive the fine moving stage  13  in the Y direction; and  26 , a stage surface plate, which plane-guides the fine moving stage  13 . 
     As shown in FIG. 3, purge plates  25   a  and  25   b  are arranged adjacent to each other around the wafer chuck  14 . The purge plates  25   a  and  25   b  are almost flush with the surface of the wafer  15 , and form a purge space around the wafer chuck  14 . 
     Similarly, an illuminance sensor purge plate  18   a  is arranged around the illuminance sensor  18 , is almost flush with the surface of the wafer  15 , and forms a purge space around the wafer chuck  14 . 
     Similarly, a stage reference mark purge plate  19   a  is arranged around the stage reference mark  19 , is almost flush with the surface of the wafer  15 , and forms a purge space around the wafer chuck  14 . 
     As shown in FIGS. 4A and 4B, slit exposure light  27  of a scan exposure type is emitted to the center of the optical path of exposure light. The wafer purge nozzle  8  is set above the exposed portion, and the space above the wafer  15  is purged with purge gas (nitrogen or the like) injected from the wafer purge nozzle  8 . An oxygen concentration of 10 ppm or less is achieved around the center of the wafer  15 . 
     The wafer  15  is surrounded by the purge plates  25   a  and  25   b , illuminance sensor purge plate  18   a , and stage reference mark purge plate  19   a . Even in exposure at the periphery of the wafer  15 , a decrease in the pressure of the purge space by the purge gas leaking from the periphery of the wafer chuck  14  can be prevented, as shown in FIGS. 5A,  5 B,  6 A, and  6 B. Gas other than purge gas does not externally enter, and purge with nitrogen serving as purge gas from the wafer purge nozzle  8  is stably performed. 
     Hence, the oxygen concentration can be maintained at 10 ppm or less in the entire region irradiated with the slit exposure light  27 . 
     (Second Embodiment) 
     FIGS. 7 to  9  are views showing the second embodiment of the present invention. 
     The second embodiment adopts, instead of the wafer chuck  14  in the first embodiment, a purge plate-integrated wafer chuck and a purge plate-integrated portion  28   a  serving as one of purge plates. The purge plate-integrated wafer chuck  28  can be detached together with the purge plate in exchanging or cleaning the wafer chuck. 
     The purge plate-integrated wafer chuck  28  is detached by a chuck exchange unit  29  shown in FIG.  9 . As shown in FIG. 9, the purge plate-integrated wafer chuck  28  is detached and exchanged by a robot having two forks. That is, the purge plate into which the two forks come can be retracted above and detached together with the wafer chuck. This structure enables automatically exchanging the wafer chuck without removing the purge plate around the wafer chuck. 
     (Third Embodiment) 
     FIGS. 10 to  12  are views showing the third embodiment of the present invention. 
     In the third embodiment, in addition to a wafer purge nozzle  8 , local purge nozzles are newly arranged on a fine moving stage  13  near the illuminance sensor  18  and stage reference mark  19  as in the first embodiment. These nozzles realize more perfect purge near the illuminance sensor  18  and stage reference mark  19 . 
     As shown in FIG. 11, an illuminance sensor purge nozzle  18   b  is formed in an illuminance sensor purge plate  18   a  for the illuminance sensor  18 . The illuminance sensor purge nozzle  18   b  injects purge gas into a gap between the illuminance sensor  18  and the illuminance sensor purge plate  18   a , thereby completely purging, with purge gas, air stagnated at the gap around the illuminance sensor  18 . 
     As shown in FIG. 12, a stage reference mark purge nozzle  19   b  is formed in a stage reference mark purge plate  19   a  for the stage reference mark  19 . The stage reference mark purge nozzle  19   b  injects purge gas into a gap between the stage reference mark  19  and the stage reference mark purge plate  19   a , thereby completely purging, with purge gas, air stagnated at the gap. 
     (Fourth Embodiment) 
     FIGS. 13 to  15 B are views showing the fourth embodiment of the present invention. 
     In the fourth embodiment, some of the purge plates in the first embodiment are integrated with an X bar mirror  16  and a Y bar mirror  17 . 
     As shown in FIG. 14, an X bar mirror purge plate  16   a  is integrated with the upper surface of the X bar mirror  16 . A Y bar mirror purge plate  17   a  is also integrated with the Y bar mirror  17 . The purge plates can be continuously formed from other purge plates. 
     As described above, according the first to fourth embodiments, flat plate members almost flush with the wafer surface are arranged adjacent to the wafer periphery. This arrangement prevents an increase in oxygen concentration caused by a purge error in exposure at the wafer periphery. Nitrogen purge can be stably performed in the whole wafer space. As a result, the exposure efficiency of the exposure apparatus using vacuum ultraviolet radiation (e.g., an F 2  laser or the like) can be increased, glass contamination can be prevented, and an exposure apparatus with high exposure stability can be implemented. 
     As described above, the purge plate can be divided at a plurality of portions. 
     (1) A purge plate is adhered to the upper surface of a bar mirror. The overhang of the purge plate between the bar mirror and the periphery of the wafer chuck can be decreased, and the flexure and vibrations of the purge plate can be reduced. 
     (2) A purge plate integrated with each sensor portion can constitute a purge plate suitable for local purge at the sensor. In, for example, exchanging the sensor, the sensor and sensor purge plate can be locally detached. 
     (3) Since the wafer chuck and some of the purge plates are integrated, all the purge plates need not be temporarily removed in exchanging the wafer chuck. The wafer chuck can be exchanged without any interference with the wafer chuck exchange robot hand. 
     Purge plates with the divided structure offer the above-mentioned merits, can reduce distortion and stress between the purge plates and the top plate of the fine moving stage, and can reduce distortion of the X and Y bar mirrors mounted on the fine moving stage. Thus, purge can be stably executed without decreasing the stage position measurement precision. At the same time, the divided structure can easily attain the flatness precision in purge plate processing, and can increase the purge space precision. 
     The purge plate is divided, and some of the divided plates are integrated with the wafer chuck or the X and Y bar mirrors. This facilitates exchanging the wafer chuck, and can increase the bar plate rigidity and stage control precision. 
     A purge nozzle for locally injecting purge gas is arranged at a portion where a hole is formed in the purge plate of the illuminance sensor, reference mark, or the like. Purge can be stably performed even in exposure near the illuminance sensor and reference mark. The purge gas consumption flow rate can be reduced by injecting local purge gas immediately before exposing a wafer portion near the illuminance sensor and reference mark. 
     (Fifth Embodiment) 
     FIGS. 23 to  28  are views showing the arrangement of the wafer stage of an exposure apparatus according to the fifth embodiment of the present invention. 
     The overall arrangement of the exposure apparatus of the fifth embodiment is the same as that of the exposure apparatus of the first embodiment shown in FIG. 1 except for the arrangement of a wafer stage  4 , and a description thereof will be omitted. 
     In FIG. 23, reference numeral  15  denotes a wafer whose single-crystal silicon substrate surface is coated with a resist in order to project and to transfer a reticle pattern drawn on a reticle substrate;  1013 , a fine moving stage, which finely adjusts the wafer  15  in the optical axis direction and tilt direction of the reduction exposure system and a rotational direction about the optical axis as a center; and  1014 , a purge plate-integrated wafer chuck, which supports and fixes the wafer  15  onto the fine moving stage  1013 . As shown in FIG. 24, the purge plate-integrated wafer chuck  1014  is constituted by integrating, with the periphery of a general disk-like wafer chuck, a purge plate, which is almost flush with the wafer  15  and formed from ceramic or the like. Reference numeral  1016  denotes an X bar mirror, which is a target mirror for measuring the X position of the fine moving stage by a laser interferometer (not shown); and  1017 , a Y bar mirror, which is a target for measuring the Y position of the fine moving stage. 
     Reference numeral  1018  denotes an illumination sensor, which is arranged on the upper surface of the fine moving stage  1013 , calibrates and measures the illuminance of exposure light before exposure, and uses the illuminance for correction of the exposure amount. 
     Reference numeral  1019  denotes a stage reference mark, which is arranged on the upper surface of the fine moving stage  1013  and has a stage alignment measurement target. Alignment of the master and wafer stage, and the like, are performed by an alignment measurement device (not shown). 
     Reference numeral  1020  denotes an X linear motor, which moves and drives the fine moving stage  1013  in the X direction;  1021 , an X guide, which moves and guides the fine moving stage  1013  in the X direction;  1022 , a Y guide, which moves and guides the X guide  1021  and fine moving stage  1013  in the Y direction;  1023  and  1024 , Y linear motors, which move and drive the fine moving stage  1013  in the Y direction; and  1026 , a stage surface plate, which plane-guides the fine moving stage  1013 . 
     An illuminance sensor purge plate  1018   a  integrated with the purge plate-integrated wafer chuck  1014  is arranged around the illuminance sensor  1018 , is almost flush with the surface of the wafer  15 , and forms a purge space around the wafer chuck  1014 . 
     Similarly, a stage reference mark purge plate  1019   a  integrated with the purge plate-integrated wafer chuck  1014  is arranged around the stage reference mark  1019 , is almost flush with the surface of the wafer  15 , and forms a purge space around the wafer chuck  1014 . 
     As shown in FIGS. 25A and 25B, slit exposure light  1027  of a scan exposure type is emitted to the center of the optical path of the exposure light. A wafer purge nozzle  8  is set above the exposed portion, and the space above the wafer  15  is purged with purge gas (nitrogen or the like) injected from the wafer purge nozzle  8 . An oxygen concentration of 10 ppm or less is achieved around the center of the wafer  15 . 
     In the purge plate-integrated wafer chuck  1014 , the purge plates are arranged around the wafer  15 . Even in exposure at the periphery of the wafer  15 , a decrease in the pressure of the purge space by purge gas leaking from the periphery of the purge plate-integrated wafer chuck  1014  can be prevented, as shown in FIGS. 26A,  26 B,  27 A, and  27 B. Gas other than purge gas does not externally enter, and purge with nitrogen serving as purge gas from the wafer purge nozzle  8  can be stably performed. 
     The oxygen concentration can, therefore, be maintained at 10 ppm or less in the entire region irradiated with the slit exposure light  1027 . 
     With the use of the purge plate-integrated wafer chuck  1014 , as shown in FIG. 28, the wafer chuck can be detached together with the purge plate in exchanging or cleaning the wafer chuck. 
     The purge plate-integrated wafer chuck  1014  is detached by a chuck exchange unit  1029  shown in FIG.  28 . As shown in FIG. 28, the purge plate-integrated wafer chuck  1014  is detached and exchanged by a robot having two forks. That is, the purge plate around the wafer chuck is retracted above and detached together with the wafer chuck. This structure allows automatically exchanging the wafer chuck without removing the purge plate around the wafer chuck. Note that an X bar mirror purge plate  1016   a , a Y bar mirror purge plate  1017   a , an illuminance sensor purge plate  1018   a , and a stage reference mark purge plate  1019   a  may be arranged integrally or separately. 
     (Sixth Embodiment) 
     The fifth embodiment has described the method of integrating the wafer chuck and purge plate by the same component. FIGS. 29A and 29B show the sixth embodiment. 
     In the sixth embodiment, a purge plate  1014   a  is arranged as another component in tight contact with the circumferential surface of a conventional wafer chuck. The entire surface in contact with the wafer chuck is coupled as a coupling portion  1014   b  by an adhesive or the like. The wafer chuck and purge plate can be integrated without any gap, similar to the first embodiment. 
     As described above, according to the fifth and sixth embodiments, flat plate members almost flush with the wafer surface are arranged adjacent to the wafer periphery. This arrangement prevents an increase in oxygen concentration caused by a purge error in exposure at the wafer periphery. Nitrogen purge can be stably performed in the whole wafer space. The exposure efficiency of the exposure apparatus using vacuum ultraviolet radiation (F 2  laser or the like) can be increased, glass contamination can be prevented, and an exposure apparatus with high exposure stability can be implemented. 
     Since the purge plate is integrated with the wafer chuck, the gap between the wafer periphery and the purge plate can be eliminated, realizing purge with high-precision purge gas. 
     The purge plate is integrated with the wafer chuck, and thus, the wafer chuck can be easily exchanged. 
     The wafer chuck and purge plate are integrated, and the bar plate rigidity and stage control precision can be increased. 
     As described above, the first to sixth embodiments can prevent a decrease in purge pressure in exposure around the wafer and an increase in oxygen concentration caused by a purge error. 
     (Seventh Embodiment) 
     A semiconductor device manufacturing process using the exposure apparatus according to the first to sixth embodiments will be explained. 
     FIG. 21 shows the flow of the whole manufacturing process of the semiconductor device. In step  1  (circuit design), a semiconductor device circuit is designed. In step  2  (mask formation), a mask is formed based on the designed circuit pattern. In step  3  (wafer formation), a wafer is formed using a material such as silicon. In step  4  (wafer process), called a pre-process, an actual circuit is formed on the wafer by lithography using the mask and wafer. Step  5  (assembly), called a post-process, is the step of forming a semiconductor chip by using the wafer formed in step  4 , and includes an assembly process (dicing and bonding) and a packaging process (chip encapsulation). In step  6  (inspection), the semiconductor device manufactured in step  5  undergoes inspections such as an operation confirmation test and a durability test. After these steps, the semiconductor device is completed and shipped (step  7 ). 
     FIG. 22 shows the detailed flow of the wafer process. In step  11  (oxidation), the wafer surface 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 vapor deposition. In step  14  (ion implantation), ions are implanted in the wafer. In step  15  (resist processing), a photosensitive agent is applied to the wafer. In step  16  (exposure), the exposure apparatus transfers a circuit pattern onto the wafer. In step  17  (developing), the exposed wafer is developed. In step  18  (etching), the resist is etched except for the developed resist image. In step  19  (resist removal), an unnecessary resist after etching is removed. These steps are repeated to form multiple circuit patterns on the wafer. 
     The present invention is not limited to the above embodiments and various changes and modifications can be made within the spirit and scope of the present invention. Therefore, to apprise the public of the scope of the present invention, the following claims are made.