Abstract:
An exposure apparatus is made so as to have respective chambers in which a main exposure system, a substrate carrying system, and a mask carrying system are housed. The apparatus is structured so that the respective environments in the chambers are substantially independently maintained from each other. Substrate processing can be facilitated by incorporating photoelectric detection of the substrate center in association with handing-over of the substrate from one substrate carrying member to another, and/or storage of a cleaning substrate in a storage member which also holds substrates being processed by the apparatus.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. 08/955,427 filed Oct. 22, 1997, which is a continuation of application Ser. No. 08/395,315 filed Feb. 28, 1995 (abandoned). 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to exposure apparatus used, for example, in fabrication process of semiconductor devices. 
     2. Related Background Art 
     The exposure apparatus used in the photolithography step for fabricating semiconductor devices is provided with a wafer loader system for performing loading and unloading of wafers. Further, the exposure apparatus is also provided with a reticle loader system for selecting a desired reticle out of a lot of reticles and setting it at an exposure position. 
     FIG. 11 is a plan view to show an exposure apparatus provided with a conventional wafer loader system. In this FIG. 11, an air-conditioning device  2  is set in a chamber  1  substantially isolated from the external atmosphere. Clean air blows from the air-conditioning device  2  through a vent pipe  3  and a HEPA filter (High Efficiency Particulate Air filter)  4  into the chamber  1  in the form of side flow, and the air having circulated in the chamber  1  then returns to the air-conditioning device  2  through a return (exhaust port)  5  and a vent pipe  6 . 
     A vibration-proof table  8  is set on a floor  7  of the chamber  1 . A wafer stage  10  for a wafer  11 A of exposure object to be mounted thereon is set on this vibration-proof table  8 . The wafer stage  10  consists mainly of a Y stage  9 Y moving in the Y direction, an X stage  9 X moving in the X direction, and a wafer holder  9 T for holding the wafer. The wafer loader system  12  is placed beside the wafer stage  10  and on the vibration-proof table  8 . The wafer loader system  12  sets (or loads) the wafer  11 A on the wafer stage  10  in such a manner that a cut portion (orientation flat portion or notch portion) formed in a part of the circumference of wafer  11 A is located in a predetermined positional relation relative to the wafer stage  10 . 
     The wafer loader system  12  is constructed in such a basic arrangement that a vertical slider body  18  extending in the Y direction is fixed on a horizontal slider body  13  extending in the X direction. Two setting tables  21 A and  21 B are provided on a side portion of the horizontal slider body  13 . Columns of storage shelves  22 A and  22 B for process wafers are mounted on the setting tables  21 A and  21 B, respectively. Wafers before exposure or wafers after exposure are stored in the columns of storage shelves  22 A and  22 B. 
     Mounted on the horizontal slider body  13  are a random access member (a wafer suction arm freely movable back and forth)  14 A for taking a wafer out of the storage shelf column  22 A, a random access member (a wafer suction arm freely movable back and forth)  14 B for taking a wafer out of the storage shelf column  22 B, a wafer hand-over member  15 , and a positioning table  16 , and a turn table  17  is provided on the positioning table  16 . Further, a carry arm  20  is set on the horizontal slider body  13  so as to be movable in the X direction. Two carry arms  19 A and  19 B are provided on the vertical slider body  18  so as to be movable in the Y direction. 
     A wafer taken out by the random access member  14 A or  14 B is carried onto the turn table  17  by the carry arm  20 . 
     FIG. 12 shows the structure of the wafer loader system  12  in FIG.  11 . As shown in this FIG. 12, a position correcting device  25  is placed above the positioning table  16 . (including the turn table  17 ). Pins (not shown) are projected from the position correcting device  25  so that they come into contact with the outer periphery of a wafer rotating on the turn table  17 . A center position of wafer and a position of the cut portion are detected based on the contact state of the pins, and, based on this detection result, the center of wafer and the position of the cut portion are set each at a predetermined position. After that, the wafer on the turn table is carried to the wafer stage by the carry arm  19 A. 
     Further, in FIG. 12, the section A shows a state wherein an in-line hand-over unit for handing over a wafer to or from a coater or a developer is provided at one end of the horizontal slider body  13 . The in-line hand-over unit herein means a carrying apparatus for carrying a wafer from a coater for or applying a photoresist to the wafer, etc. to the exposure apparatus, or a carrying apparatus for carrying a wafer after exposure from the exposure apparatus to a developing apparatus (developer) etc. The section B shows a state wherein a random access member  14 C and a setting table  21 C having a column of wafer storage shelves are added to the wafer loader system  12 . The section C shows a state wherein an in-line hand-over unit is provided at the other end of the horizontal slider body  13 . 
     Returning to FIG. 11, a first in-line hand-over unit  23  is composed of an arm  23   a  and a slide shaft  23   b , and a second in-line hand-over unit  24  is composed of an arm  24   a , a slide shaft  24   b , and a rotary member  24   c . After the arm  23   a  of the in-line hand-over unit  23  receives a wafer  11 B from a coater or a developer (not shown), the wafer  11 B is handed over to the carry arm  20  at position P 1  . Similarly, after the arm  24   a  of the in-line hand-over unit  24  receives a wafer  11 C from a coater or a developer (not shown), the wafer  11 C is handed over to the carry arm  20  via position P 2  and position P 3 . Or, conversely, a wafer is handed over from the in-line hand-over unit  23  or  24  to the coater or developer (not shown). 
     In the above wafer loader system  12 , the carry arm  20 , carry arm  19 A, carry arm  19 B, arm  23   a , arm  24   a , random access members  14 A,  14 B, positioning table  16 , and turn table  17  each were made of alumina ceramics, (containing 95 or more % of Al 2 O 3 ), and plastic storage shelves (which can store twenty five wafers) mainly used in actual processes have been used as a substitute for the wafer storage shelves  22 A and  22 B. 
     In addition to the wafer loader system  12 , a reticle loader system (not shown) was also set on the vibration-proof table  8 . The reticle loader system is arranged to take a desired reticle out of a reticle case and to set it at the exposure position. 
     In the conventional technology as described above, because the wafer loader system  12  was set together with the wafer stage  10  on the vibration-proof table  8 , vibration occurring upon carrying the wafer by the wafer loader system  12  was transferred to the wafer stage  10 , which could degrade the positioning accuracy of wafer stage  10 . 
     Since the wafer loader system or the reticle carrying system and the wafer stage  10  are set in the same chamber  1  actuation of the carrying mechanism can allow allowed dust to be mixed about the wafer stage  10  and can change the ambient temperature thereof. 
     Further, because the air conditioning of the whole inside of the chamber  1  was effected by one air-conditioning device  2  and a set of HEPA filter  4  and return  5 , there were cases that necessary air-conditioning performance was not achieved at each of the exposure portion of the horizontal slider body  13  of the wafer loader system  12 , and the reticle loader system, etc., or that the air conditioning exceeded specifications. 
     With respect to this, for example, if the wafer loader system  12  was located on the windward side of the exposure system, there were cases that particles caused by the wafer loader system  12 , or a temperature change in this system negatively affected the exposure system on the leeward side. 
     Further, as shown in FIG. 11, when a wafer was handed over to or from the coater or developer, it was necessary to install the in-line hand-over units  23  and  24  etc. for exclusive use, which complicated the whole structure and which caused dust production because of an increase in the number of wafer hand-overs. 
     Also, high-accuracy positioning was difficult, because, in loading a wafer on the wafer stage  10 , the wafer positioning was carried out by a method of bringing the pins actually in contact with the wafer on the turn table  17 . Thus, the conventional technology required wafer re-positioning after setting the wafer on the wafer stage  10 , correcting the wafer position while moving the X stage  9 X or the Y stage  9 Y, or by floating the wafer over the wafer stage  10  by air flow and then pushing the wafer against a positioning member, which complicated the control and caused the problem of dust production due to the air flow, etc. 
     Additionally, because the carry arm  20  and other components were made of alumina ceramics (containing 95 or more % of Al 2 O 3 ) or a resin, there was a problem of adhesion of dust due to charge on the wafer or carry arm, etc. Similarly, because the wafer storage shelves  22 A,  22 B were also made of a resin for process, there were problems of adhesion of dust due to the charge as described above, access errors of wafer due to deformation of a shelf, etc. 
     Still further, there was another problem that when the resist dropped from the edge portion or the back surface of a wafer inside the storage shelves  22 A,  22 B, fine particles were adhered to wafers on lower shelves. Since an operator took out or brought in a cleaning substrate having the form of a thin disk in order to clean a wafer carrying surface and a contact surface of wafer holder  9 T with the wafer, a long time period was necessary for cleaning, which lowered the apparatus operating efficiency and which caused a temperature change in the chamber or mixture of fine particles. 
     SUMMARY OF THE INVENTION 
     In view of the above-described points, an object of the present invention is to provide exposure apparatus with high reliability and high efficiency. 
     To achieve the above object, an exposure apparatus of the present invention may comprise a main exposure system for transferring a pattern on a mask set at a predetermined position, onto a photosensitive substrate, a substrate carrying system for loading the photosensitive substrate into the main exposure system and unloading the photosensitive substrate from the main exposure system, and a mask carrying system for loading the mask at said predetermined position and unloading the mask from said predetermined position, wherein the three systems are set in respective chambers independent of each other. 
     This arrangement can reduce vibration generated by the substrate carrying system or the mask carrying system, or the influence of dust etc. on the main exposure system. 
     To achieve the above object, an exposure apparatus of the present invention is preferably so arranged that a substrate holding hand rotatable about a predetermined axis and telescopically movable in the radial direction from said predetermined axis is provided in the substrate carrying system for loading or unloading the photosensitive substrate in or from the main exposure system for transferring the pattern on the mask, onto the photosensitive substrate, whereby this substrate holding hand is used to unload the photosensitive substrate out of the exposure system chamber or to load the photosensitive substrate from outside the exposure system chamber. 
     This arrangement permits hand-over of a photosensitive substrate with respect to a coater or developer etc. without separately setting an in-line hand-over unit, which can simplify the apparatus structure and which can lower production of dust etc. because of a decrease in the number of hand-over of photosensitive substrates. 
     Further, to achieve the above object, an exposure apparatus of the present invention is preferably so arranged that the substrate carrying system, for loading or unloading the photosensitive substrate in or from the main exposure system for transferring the pattern on the mask onto the photosensitive substrate, comprises a first carry member for carrying the photosensitive substrate in a first direction, a second carry member for carrying the photosensitive substrate in a second direction intersecting with the first direction in order to load the photosensitive substrate in the main exposure system and to unload the photosensitive substrate from the main exposure system, and a position detector for photoelectrically detecting a position of the center of the photosensitive substrate. 
     According to such an arrangement, the photosensitive substrate can be handed over from the first carry member to the second carry member after the center position of the photosensitive substrate is detected without contact with the photosensitive substrate and at high speed. 
     To achieve the above object, an exposure apparatus of the present invention comprises a main exposure system for transferring a pattern on a mask, onto a photosensitive substrate, a substrate carrying system for loading the photosensitive substrate in the main exposure system and unloading the photosensitive substrate from the main exposure system, a first base on which the main exposure system is set, and a second base, independent of the first base, on which the substrate carrying system is set. 
     This arrangement makes the vibration generated upon actuation of the substrate carrying system unlikely to be transferred to the main exposure system. 
     Further, in order to achieve the above object, an exposure apparatus of the present invention may comprise a main exposure system for transferring a pattern on a mask, onto a photosensitive substrate, a substrate carrying system for loading the photosensitive substrate in the main exposure system and unloading the photosensitive substrate from the main exposure system, a first vacuum pump for providing to hold the photosensitive substrate in the main exposure system, and a second vacuum pump independent of the first vacuum pump, for providing to hold the photosensitive substrate in the substrate carrying system. 
     This arrangement can prevent pressure variations caused upon suction or separation of the photosensitive substrate in the substrate carrying system from affecting the suction holding of the photosensitive substrate in the main exposure system. Conversely, when suction or separation of the photosensitive substrate is carried out in the main exposure system, the suction holding of the photosensitive substrate in the substrate carrying system will not be affected thereby, either. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional plan view to showing a layout in a chamber, of a first embodiment of the exposure apparatus according to the present invention; 
     FIG. 2 is a cross section taken along line  2 — 2  in FIG. 1; 
     FIG. 3 is an enlarged view of section B in FIG. 1; 
     FIG. 4 is a view observed in the direction of arrows along line  4 — 4  in FIG. 3; 
     FIG. 5 is an enlarged view observed in the direction D of FIG. 1; 
     FIG. 6 is a cross section taken along line  6 — 6  in FIG. 5; 
     FIG. 7 is a cross section taken along line  7 — 7  in FIG. 3; 
     FIG. 8 is an enlarged plan view to showing another example of sensors near an adjustment table  51  in the first embodiment; 
     FIG. 9 is a cross-sectional plan view to showing a layout in a chamber, of a second embodiment of the exposure apparatus according to the present invention; 
     FIG. 10 is an enlarged plan view of section G in FIG. 9; 
     FIG. 11 is a plan view to showing an exposure apparatus provided with a conventional wafer loader system; and 
     FIG. 12 is a perspective view to showing structure of the wafer loader system  12  in FIG.  11 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The first embodiment of the exposure apparatus according to the present invention will be described with reference to the accompanying drawings. 
     FIG. 1 is a cross-sectional plan view of a chamber in the exposure apparatus of the present embodiment. In FIG. 1, three independent chambers  31 ,  32 , and  33  are juxtaposed. FIG. 2 is a cross section taken along line  2 — 2  in FIG. 1, and, as shown in this FIG. 2, the third independent chamber  33  is separated into a lower chamber  33 A and an upper chamber  33 B by a compartment plate  33   a.    
     An air-conditioning device  34  consisting of three air-conditioning units, operating independently of each other, is set in the first independent chamber  31 . Air temperature-controlled by the first air-conditioning unit in the air-conditioning device  34  blows through a first pipe  35 A and a dust-removing HEPA filter  59 A (FIG. 2) set on the ceiling of the second independent chamber  32  into the independent chamber  32 , and then returns to the first air-conditioning unit through a return  60 A set on the floor of independent chamber  32 , and a first pipe  36 A. Also, air temperature-controlled by the second air-conditioning unit in the air-conditioning device  34 , is guided through a second pipe  35 B to a HEPA filter  59 C set on the ceiling of the lower chamber  33 A of the third independent chamber  33 . Then, the air flowing down into the lower chamber  33 A to reaches a return  60 C set on the floor of the lower chamber  33 A and returns to the second air-conditioning unit through a second pipe  36 B. Further, air temperature-controlled by the third air-conditioning unit is guided through a third pipe  35 C to a HEPA filter  59 B set on the ceiling of the upper chamber  33 B of the independent chamber  33 . Then, the air flowing down into the upper chamber  33 B reaches a return  60 B set on the floor and returns to the third air-conditioning unit through a third pipe  36 C. 
     Although not shown, it is preferable that a chemical filter be provided together with the HEPA filters  59 A- 59 C in order to prevent existing ions (for example NH 4   + , SO 4   2− ), sulfur dioxide (SO 2 ), etc. from intruding into the independent chambers  32 ,  33 A,  33 B in which the main exposure system, the wafer loader system, etc. are set. This can prevent a phenomenon to decrease the reflectivity or transmittance of an illumination optical system due to production of ammonium sulfate ((NH 4 ) 2 SO 4 ) etc. adhering to optical elements constituting the illumination optical system, and can also prevent occurrence of such a phenomenon that a cross section of resist pattern acquires a T shape. The chemical filter is preferably provided corresponding to each of the three HEPA filters  59 A- 59 C. It is also conceivable that the chemical filter is provided at least for the HEPA filter  59 A but not for the other HEPA filters  59 B,  59 C. 
     In FIG. 2, the main exposure system is set in the second independent chamber  32 . Namely, a vibration-proof table  37  is set through vibration-proof pads  37   a  and  37   b  on the floor of independent chamber  32 , and then the wafer stage  10  is placed on the vibration-proof table  37 . A wafer  11 A coated with a photoresist is loaded on the wafer stage  10  upon exposure. A column  62  is planted on the vibration-proof table  37 . A projection optical system  63  is fixed in the middle part of column  62 , and a reticle  64 A as an exposure object is mounted on the reticle holder at the top end of the column  62 . 
     Returning to FIG. 1, the wafer stage  10  is composed mainly of a base  9 B, a Y stage  9 Y, an X stage  9 X, and a wafer holder  9 T. The wafer  11 A is held as an exposure object by vacuum suction on the wafer holder  9 T. A cut portion, which is called an orientation flat (or notch), is formed in a part of the circular circumference of wafer  11 A, and the wafer  11 A is loaded on the wafer holder  9 T so that this cut portion is directed in a predetermined direction and so that the center of wafer  11 A is located in a predetermined positional relation relative to the wafer holder  9 T. 
     In the present embodiment the wafer loader system  38  is provided for loading a wafer onto the wafer holder  9 T and for unloading the wafer from the wafer holder  9 T. The wafer loader system  38  is placed on the floor in the lower chamber  33 A (FIG. 2) of the third independent chamber  33 . 
     A guide of the wafer loader system  38  is composed of a horizontal slider body  39  extending in the X direction and a vertical slider body  48  extending in the Y direction. A scalar robot hand  47  is set on the horizontal slider body  39  so as to be slidable in the X direction. The scalar robot hand  47  consists of an X-axis moving member  41  for moving in the X direction along the horizontal slider body  39 , a Z-axis moving member  42  for telescopically moving in the Z direction perpendicular to the XY plane on the X-axis moving member  41 , a θ-axis rotating member  43  for rotating about the center  42   a  of the Z-axis moving member  42 , an R-axis rotating member  44  arranged as rotatable at the distal end of the θ-axis rotating member  43 , and a hand member  45  arranged as rotatable at the distal end of the R-axis rotating member  44 , in which a vacuum suction portion  46  is attached to the distal end of the hand member  45 . Rotating the θ-axis rotating member  43  about the center  42   a , the hand member  45  rotates in the θ direction, whereby, combining rotation angles of the R-axis rotating member  44  and hand member  45  with each other, the position can be adjusted in the radial direction (in the R direction) from the center  42   a  of the hand member  45 . 
     Further, setting tables  21 A and  54  are provided on a side of the horizontal slider body  39 , and columns of storage shelves  22 A and  55  for storing wafers are set on the setting tables  21 A and  54 , respectively. Moreover, temporary wafer-placing tables  56 A and  56 B are set on the side of the horizontal slider body  39  for a wafer to be temporarily mounted thereon. A plurality of pins (four pins in FIG. 1) for wafer mounting are planted on each of the temporary placing tables  56 A and  56 B. Openings  33   d  and  33   e  for exchange of storage shelves etc. with the outside are provided on the side surface of the independent chamber  33  near the storage shelves  22 A and  55  and near the temporary placing tables  56 A and  56 B, respectively for exchange of storage shelves, etc. In addition, an opening  33   c  is provided on the side surface of the independent chamber  33  near the left end of the horizontal slider body  38 , so that by the hand portion  45  of the scalar robot hand  47  in and out through the opening  33   c , a wafer  11 D can be handed over to or from an external device (a coater of photoresist or a developing device, etc. set outside) and a wafer  11 E can be handed over at another position Q 1 . Further, an opening  33   f  is provided on the side surface of the independent chamber  33  near the right end of the horizontal slider body  38 , so that by, moving the scalar robot hand  47  to a position Q 7  and projecting the hand portion through the opening  33   f , a wafer  11 F can be handed over to or from an external device and another wafer  11 G can be handed over at another position Q 8 . Similarly, by moving the scalar robot hand  47  to a position Q 3 , Q 5 , or Q 6 , a wafer can be handed over to or from the column of storage shelves  55 , temporary placing table  56 A, or the temporary placing table  56 B, respectively. 
     The vertical slider body  48  projects into the independent chamber  32  through an opening  32   a  on the side surface of the independent chamber  32  and an opening  33   b  on the side surface of the lower chamber  33 A of the independent chamber  33 . Two sliders  49 A and  49 B, each with a wafer contact portion having a C shape, are attached to the side surface of the vertical slider body  48  so as to be slidable in the longitudinal direction. These two sliders  49 A and  49 B each independently move between the independent chamber  32  and the lower chamber  33 A while holding a wafer by vacuum suction. 
     The scalar robot hand  47  takes a wafer out of the storage shelves  55 , for example, and thereafter hands over the wafer at position Q 4  through the turn table  52  movable up and down, to the slider  49 A or  49 B. After that, the scalar robot hand  47  receives a wafer, after exposure, from the slider  49 A or  49 B similarly through an up and down motion of the turn table  52  and then returns the wafer thus received for storage such as to the storage shelves  55 . 
     The portions which contact the wafer such as, the hand portion  45  of the scalar robot hand  47 , the slider  49 A, and the slider  49 B, are formed of conductive ceramics having a fine surface. Alternatively, surfaces of wafer contact portions may be coated with a coating etc. of conductive ceramics with a fine surface. 
     When the wafer contact portions are formed of conductive ceramics, the following operational effects can be achieved: (1) production of dust is reduced because of decreased contacts with the photosensitive substrate; (2) charge on the contact portions and the photosensitive substrate is avoided so as to reduce the dust collecting effect; (3) static electricity on a charged photosensitive substrate is removed so as to prevent electrostatic discharge failure of photosensitive substrate and to reduce the dust collecting effect of the photosensitive substrate; and (4) because the contact portions are fine, the anchor effect (drawing effect) upon adhesion of particles (fine particulates) is reduced so as to facilitate cleaning. 
     In FIG. 1 a sensor table  50  is set near a region where the horizontal slider body  39  and the vertical slider body  48  intersect with each other, i.e., near the position Q 4 . A center position sensor (as described hereinafter) for detecting a position of the wafer center is placed on this sensor table  50 . An adjustment table  51  is placed near the sensor table  50 . A conductive ceramic turn table  52  is provided above the adjustment table  51  so as to be rotatable about an axis perpendicular to the XY plane. There are a light-projecting device  53  in a cut detection sensor for detecting a position of the linear cut portion (orientation flat) in the wafer circumference, and a line sensor  75  consisting mainly of a one-dimensional CCD (FIG.  2 ), as arranged on the adjustment table  51  and at a position between the turn table  52  and the sensor table  50 . The light-projecting device  53  projects a slit light beam to which the photoresist on the wafer is not sensitive, toward the line sensor  75 , and the line sensor  75  detects a length of a shielded portion in the slit light beam to supply the detection result to an unrepresented control system. 
     FIG. 3 is an enlarged view of the portion B near the region where the horizontal slider body  39  and vertical slider body  48  intersect with each other in FIG.  1 . In FIG. 3, when the wafer  11 J is handed over from the scalar robot hand  47  onto the turn table  52 , the wafer  11 J first passes inside the sensor table  50 . As shown in FIG. 4, which is a cross section taken along  4 — 4  line in FIG. 3, there are four light-projecting devices  76 A- 76 D provided in the upper portion of sensor table  50 , and four light-receiving devices  78 A- 78 D arranged as opposed to the light-projecting devices in the lower portion of sensor table  50 . The wafer  11 J passes between those light-projecting devices  76 A- 76 D and light-receiving devices  78 A- 78 D. Each light-projecting device  76 A- 76 D emits a beam of illumination light to which the photoresist on the wafer is not sensitive. 
     In this case, because the wafer  11 J is substantially circular as shown in FIG. 3, the position of the center of wafer  11 J can be obtained by the unrepresented control system from a relation between a position of wafer  11 J in the direction to the turn table  52  and a timing between the moment when the light is shielded by the wafer  11 J in each of the light-receiving devices  78 A- 78 D in FIG.  4  and the moment when the light is received. Then the scalar robot hand  47  places the wafer  11 J on the turn table  52  so that the position of the center of wafer  11 J coincides with the rotational center of the turn table  52 . On this occasion the slider  49 A is moved to below the wafer  11 J. Based on the information on the center position, the wafer  11 J is mounted on the turn table  52  with their centers matching with each other by controlling the R axis and the θ axis (or the X axis) of the scalar robot hand  47 . The wafer  11 J is vacuum-sucked on the turn table  52 . According to the above positioning method, the wafer center is positioned relative to the center of turn table  52  approximately at the accuracy of about ±0.2 mm. 
     Rotating the turn table  52  in that state, the peripheral edge of wafer  11 J rotates between the light-projecting device  53  and the line sensor  75  (FIG. 2) in the cut detection sensor. Since the length of the light-shielded portion is decreased when the cut portion (orientation flat or notch) of wafer  11   j  passes over the line sensor  75 , whereby the unrepresented control system can detect the position of the but portion of wafer  11 J. According to this detection result, the rotation of the turn table  52  is stopped at a position where the cut portion of wafer  11 J is opposed for example to the horizontal slider body  39 . After that, the suction of wafer  11 J by the turn table  52  is released, and the turn table  52  is lowered. Then, the wafer  11 J is vacuum-sucked on the surface of slider  49 A, and the slider  49 A is moved along the vertical slider body  48  to the independent chamber  32  in FIG.  1 . Then, the wafer  11 J is transferred from the slider  49 A to the wafer holder  9 T by an unrepresented wafer hand-over means (which may be for example movable pins provided in the wafer holder  9 T, being movable up and down (in the direction perpendicular to the plane of FIG. 1) and having a surface in which a groove for vacuum suction is formed). On this occasion, the wafer  11 J is mounted on the wafer holder  9 T while the center of wafer  11 J and the location of the cut portion each are accurately set in a predetermined state. 
     Further, there are generally concentric protrusions on the wafer holder  9 T and the wafer  11 J is mounted on these concentric protrusions. It is thus desired that the contact portions of the scalar robot hand  47  and the sliders  49 A,  49 B with the wafer  11 J be differentiated from the contact portions on the wafer holder  9 T. Namely, positions on the back wafer surface in contact with the scalar robot hand  47  and the sliders  49 A,  49 B are made different from positions on the back wafer surface in contact with the projections of wafer holder  9 T. In this case, the positions and areas of the contact portions of the scalar robot hand  47  and the sliders  49 A,  49 B with wafer can be determined according to the shape of the protrusions of wafer holder  9 T. By this, the flatness of wafer on the wafer holder  9 T can be well maintained. The reason is as follows. Even if a foreign material is adhered to the back wafer surface because of the contact with the scalar robot hand  47  and the sliders  49 A,  49 B, the foreign material will never be sandwiched between the protrusions of wafer holder  9 T and the wafer. 
     The line sensor  75  of FIG. 2 may be replaced by an analog sensor wherein a cylindrical lens is combined with a light-receiving element (for example a photodiode). With use of this analog sensor a quantity of received light of the light-receiving element changes depending upon the length of the light-shielded portion by the wafer, whereby the length of the light-shielded portion can be detected. Also, the positioning of the cut portion (orientation flat or notch) of wafer  11 J may be carried out in such a manner that two pairs of light-projecting devices  53  and analog sensors are arranged at two respective locations in the circumferential direction of wafer and that the rotational position of turn table  52  is fixed by the servo method so as to balance output signals from the two analog sensors. 
     Returning to FIG. 3, above the adjustment table  51  there is a light guide  77  for guiding light obtained by separating part of the exposure light for illuminating the reticle. 
     FIG. 7 is a cross section taken along  7 — 7  line in FIG.  3 . As shown in this FIG. 7, an emission end  77   a  of the light guide  77  is attached to an upper end of a moving C-shape table  85 . A line sensor  84 , consisting of a one-dimensional CCD, is fixed to the lower end, of the moving table  85  so as to be opposed to the emission end  77   a . A slider  85   a  fixed to the bottom surface of the moving table  85  is set in a guide member on a support table  86  fixed to the adjustment table  51 . A drive motor  87  is fixed to the support table  86 , a feed screw  88  is screwed in a side of the moving table  85  in parallel with the sliding direction of slider  85   a , and the feed screw  88  is coupled through a coupling  89  with a rotational shaft of the drive motor  87 . The moving table  85  moves in the radial direction with respective to the center of the turn table  52 . With actuation of the drive motor  87 , the moving table  85  is moved along the radial direction. 
     Upon so-called peripheral exposure, the slit exposure light, to which the photoresist laid on the wafer  11 J is sensitive, is emitted from the emission end  77   a  of the light guide  77  toward the peripheral edge of wafer  11 J sucked on the turn table,  52 , and the line sensor  84  detects the length of the light-shielded portion of the exposure light to supply the detection result to the unrepresented control system. The peripheral exposure herein means that only the photoresist at the peripheral edge of wafer  11 J is exposed to the exposure light in order to prevent dust from being produced from the peripheral edge of wafer  11 J. In this case, because the present embodiment is so arranged that the rotational center of turn table  52  is substantially accurately coincident with the center of wafer  11 J, the width of the peripheral exposure of wafer  11 J can be accurately set to a desired value by adjusting the position of the moving table  85  and then emitting the exposure light from the emission end  77   a . Since the position of the cut of wafer is known, an encoder-added motor or a stepping motor may be employed for the turn table  52  to adjust the position of the moving table  85  so as to keep the width of peripheral exposure constant when the cut portion of wafer  11 J reaches between the exit end  77   a  and the line sensor  84 , whereby the peripheral exposure can be effected in the constant width even in the cut portion of wafer  11   j.    
     Returning to FIG. 2, the reticle loader system  65  is placed on the return  60 B in the upper chamber  33 B of the independent chamber  33 . A guide of the reticle loader system  65  consists of a vertical slider body  72  projecting through an opening  32   b  of the independent chamber  32  and an opening  33   g  of the upper chamber  33 B into the independent chamber  32 , and two sliders  73 A and  73 B are attached to the vertical slider body  72  so as to be slidable along the vertical slider body  72 . Installed near a support table of the vertical slider body  72  is a scalar robot hand consisting of a base  66 , a Z-axis moving member  67  for telescopically moving in the Z direction perpendicular to the XY plane on the base  66 , a θ-axis rotating member  68  for rotating about the Z-axis moving member  67 , an R-axis rotating member  69  arranged as rotatable at the distal end of this θ-axis rotating member  68 , and a hand member  70  arranged as rotatable at the distal end of the R-axis rotating member  69 . 
     As will be appreciated especially from FIG. 2, the adjacent sidewalls  32 S and  33 S of chambers  32  and  33  constitute respective compartment members which spatially separate the main exposure system from the wafer loader system  38  and the reticle loader system  65 . 
     A column of storage shelves  74  for reticles is set near the scalar robot hand for reticles. The hand member  70  of the scalar robot hand takes a reticle by vacuum suction from the storage shelves  74  and hands over the thus taken reticle to the slider  73 A or  73 B of the vertical slider body. After that, while holding the reticle by vacuum suction, the slider  73 A or  73 B moves along the vertical slider body  72  into the independent chamber  32  and then sets the reticle on the reticle holder on the column  62  of the main exposure system through an unrepresented reticle hand-over means. When a reticle is exchanged for another, the reticle taken out of the reticle holder is returned through the slider  73 A or  73 B and the scalar robot hand for reticles to the storage shelves  74 . Since the scalar robot hand is also used for carrying the reticle as described, the reticle loader system  65  is simplified. 
     Further, in FIG. 2, vacuum pumps  61 A,  61 C, and  61 B are set in the second independent chamber  32 , the lower chamber  33 A of the third independent chamber  33 , and the upper chamber  33 B, respectively, so that the vacuum pump  61 A supplies a negative pressure for vacuum suction in the main exposure system in the independent chamber  32 , the vacuum pump  61 C supplies a negative pressure for vacuum suction in the wafer loader system  38  in the chamber  33 A, and the vacuum pump  61 B supplies a negative pressure for vacuum suction in the reticle loader system  65  in the chamber  33 B. As described, the present embodiment is arranged to perform the vacuum suction in the main exposure system, the vacuum suction in the wafer loader system  38 , and the vacuum suction in the reticle loader system  65  independently of each other, thus presenting an advantage that there is no influence of suction or separation of wafer transferred between the systems. While a reticle pattern is projected onto a wafer sucked on the wafer holder  9 T of the main exposure system in the independent chamber  32 , there is no pressure change on the side of wafer holder  9 T even with start or stop of vacuum suction in the wafer loader system  38  or the reticle loader system  65 , thus presenting an advantage that no wafer positional deviation occurs. 
     The structure of the column of storage shelves  55  in FIG. 1 is next described in detail referring to FIG.  5  and FIG.  6 . FIG. 5 is a view observed in the direction of arrow D in FIG.  1 . As shown in FIG. 5, the column of storage shelves  55  is a box made of a conductive material, having neither front wall nor back wall. There are compartment plates  79   1 ,  79   2 , . . . of a conductive material unitedly incorporated in order in the box between the top plate and the bottom plate  79   N  of the box. This arrangement allows N wafers to be stored in the storage shelves  55 , where an example of N is (25×n+1) using an integer n≧1. That is, the number of wafers is  26 ,  51 ,  76 , . . . If n=0, N is 1. 
     Further, the column of storage shelves  55  is fixed by screwing on the setting table  54 , and three conductive ceramic pins  80 A,  81 A,  82 A are planted on the compartment plate  79   1  in the storage shelves  55 . Similarly, three conductive ceramic pins are planted on each of the other compartment plates  79   2 ,  79   3 , . . . , and the bottom plate  79   N . For example, in the case of exposure for one lot of wafers, wafers  11   1 ,  11   2 , . . . ,  11   N  are set on the compartment plates  79   1 ,  79   2 , . . . , and the bottom plate  79   N , respectively. 
     As described, because the column of storage shelves  55  is made of a conductive material, the adhesion of dust etc. to the storage shelves and wafers can be reduced. Since the compartment plates are provided in the storage shelves  55 , accidents in which dust produced from the back surface or edge portion of a wafer on an upper shelf might drop to attach to another wafer, on a lower shelf, can be prevented. 
     For example, when a wafer  11   1  is taken out of the storage shelves  55 , the hand member  45  of the scalar robot hand  47  is put between the back face of wafer  11   1  and the compartment plate  79   1 , as shown in FIG. 6, which is a cross section taken along  6 — 6  line in FIG. 5, and then the wafer  11   1  is taken out. 
     In the present embodiment, because the number of wafers in one lot upon normal exposure is 25×n, the storage shelves  55  of the present embodiment can store one more wafer. The number of wafers may be increased for more extra wafers to be stored. The shelf for the extra wafer may be used to store, for example, a reference wafer of high flatness for measurement of flatness on the wafer holder  9 T (FIG.  1 ), a mask wafer for self-measurement (inspection) of apparatus, or a wafer for cleaning the contact portions with wafer, etc. Although the present embodiment is so arranged that the space for storing the extra wafer is secured in a part of the storage shelves  55 , another arrangement may employ an independent table, such as the temporary placing tables  56 A,  56 B in FIG.  1 . 
     Since the inspection wafer or cleaning wafer is stored in the apparatus, the operator does not need to take the inspection wafer or cleaning wafer in and out, which improves the operating efficiency, of exposure apparatus and which can prevent intrusion of dust into the chamber and the temperature change in the chamber. 
     Since the column of storage shelves  55  of the present embodiment is open both on the front and back sides, inspection light can pass from the front or back. Then, as shown in FIG. 1, a light projector  57  and a light receiver  58  are set on either side of the storage shelves  55  on the inner side surface of chamber. A light beam emitted from the light projector  57  passes through the storage shelves  55  if there is not a wafer in the storage shelf  55 , thus being received by the light receiver  58 ; the light beam is interrupted if there is a wafer. This can check presence or absence of a wafer in the storage shelves  55 . Further, this function can also be achieved even if the column of storage shelves  55  has a back wall insofar as it is a transparent body. 
     Although the column of storage shelves  55  is fixed by screwing on the setting table  54  as shown in FIG. 5, the storage shelves  55  may be fixed by a lock mechanism which is freely opened and closed. With such a lock mechanism provided, even conventional storage, shelves  22  for process wafers (FIG. 1) can also be fixed on the setting table  55 . 
     The above embodiment was so arranged, as shown, in FIG. 3, that the sensors in the sensor table  50 , and the cut sensor including the light-projecting device  53  detected the center position of wafer  11 J and the position of the cut portion (orientation flat or notch), respectively. The detection, however, may be effected by such an arrangement, as shown in FIG. 8, that light-projecting devices  90 A- 90 D each for emitting a slit light beam downward are fixed at four locations above the adjustment table  51  and that line sensors are set as opposed to these light-projecting devices  90 A- 90 D with the peripheral edge of wafer  11 J disposed therebetween. In this case, the center position of wafer  11 J can be roughly positioned at the center position of turn table  52  by driving and positioning the hand member  45  of the scalar robot hand by the servo method in the R direction, in the θ direction, or in the X direction so as to locate edge portions of wafer  11 J at predetermined positions on the respective line sensors. 
     For example, using the light-projecting device  90 A and the line sensor opposed thereto among the four combinations of light-projecting devices and line sensors, the cut portion (orientation flat or notch) of wafer  11 J can also be detected. In this case, because there are four line sensors, the position of the cut portion can be detected rotating the wafer  11 J at most about 90° from any direction to which the cut portion of wafer  11 J is directed. The same positioning can be performed if there are two or more combinations of light-projecting devices and line sensors. 
     The second embodiment of the present invention is next described referring to FIG.  9  and FIG.  10 . This embodiment is a modification of the embodiment of FIG. 1 wherein the length of the horizontal slider body  39  in the wafer loader system  38  is made shorter and, therefore, portions corresponding to those in FIG.  1  and FIG. 3 are denoted by the same reference numerals, with detailed description thereof accordingly omitted. 
     FIG. 9 is a plan view of the inside of the chamber in the second embodiment. In FIG. 9, the wafer loader system is set in the lower chamber of the third independent chamber  33 . The X-directional guide of the wafer loader system is a horizontal slider body  39 A, shorter than that in the first embodiment. A scalar robot hand  47  for holding a wafer is mounted on the horizontal slider body  39 A so as to be slidable in the X direction along the horizontal slider body  39 A. A wafer  11 D or  11 E can be handed over through an opening on the left side surface of chamber by the scalar robot hand  47 , and a wafer can also be handed over from or to the storage shelves  55  or  22 A. 
     The sensor table  50  is placed in the vicinity of the right end of the horizontal slider body  39 A and four sets of light-projecting devices and light-receiving devices are arranged in the sensor table  50 , similarly as in FIG.  4 . Further, the adjustment table  51  is set on the right side of the sensor table  50 . A turn table  52  is attached onto the adjustment table  51  so as to be rotatable. A detection sensor for detecting the cut wafer portion (orientation flat or notch), consisting of a light-projecting device  53 , is attached to the front side surface of the adjustment table  51 . In the present embodiment the vertical slider body  48  is set further right of the adjustment table  51 . Sliders  49 A and  49 B are attached to the vertical slider body  48  so as to be slidable along the vertical slider body  48 . A peripheral exposure portion including the light guide  77  is installed between the adjustment table  51  and the vertical slider body  48 . The structure of the other parts is the same as in the first embodiment. 
     In the present embodiment, the wafer received by the scalar robot hand  47  is set on the turn table  52  after being positioned at the right end of the horizontal slider body  39 A. 
     FIG. 10 is an enlarged view of section G near the adjustment table  51  in FIG.  9 . As shown in FIG. 10, when the scalar robot hand  47  hands over the wafer  11 J onto the turn table  52  at the right end of the horizontal slider body  39 A, the sensor table  50  detects the center position of wafer  11 J and the cut sensor including the light-projecting device  53  detects the position of the cut portion of wafer  11 J. The peripheral exposure of wafer  11 J is performed with necessity by the peripheral exposure system including the light guide  77 . After that, the wafer  11 J is handed over to the slider  49 A and then is transferred to the main exposure system. According to this second embodiment, the wafer loader system is made compact. 
     It should be noted that the present invention is by no means limited to the above-described embodiments but may include a variety of arrangements within the scope not departing from the essence of the present invention, of course.