Abstract:
An exposure apparatus for performing exposure of a substrate to light via a reticle. The apparatus includes a first stage configured to hold a chuck. The chuck has a support base with an electrode, and forms a container, for one of the substrate and the reticle, together with a cover. The container electrostatically chucks the one on the support base by the electrode. A transporter transports the container in which the one is contained, and loads the chuck, which chucks the one, on the first stage without the cover. A second stage holds the other of the substrate and the reticle. The apparatus obtains a first positional shift amount between the chuck and the one chucked on the chuck before the transportation by the transporter, to measure a second positional shift amount between a reference mark on the chuck held by the first stage and a reference mark on the second stage, and corrects positions of the first and second stages based on the first and second positional shift amounts, to perform the exposure.

Description:
This application claims the benefit of Japanese Patent Application No. 2005-193084, filed on Jun. 30, 2005, which is hereby incorporated by reference herein in its entirety. 
   FIELD OF THE INVENTION 
   The present invention relates to a container for accommodating a substrate, such as a mask or a wafer, and a method of transporting the substrate using the same. 
   BACKGROUND OF THE INVENTION 
   In the exposure step of a semiconductor manufacturing process, a circuit pattern is formed on a reticle (photomask) is projected and exposed onto a wafer applied with a resist material to form a latent image pattern on the resist material. The latent image pattern is developed thereafter to form a resist pattern for etching, ion implantation, and the like. 
   If a particle, or the like, is present on the reticle, the particle, together with the pattern, is transferred onto the wafer to cause an error. In order to prevent this, a pattern protective member (including, e.g., a film-like synthetic resin member or a plate-like member made of silica glass, or the like), called a pellicle, is attached to the reticle. 
   The pellicle is arranged at a position offset from the pattern surface of the reticle by a predetermined distance and supported by a pellicle support frame. When the pellicle is used, a particle attaches to a pellicle surface offset from the pattern surface of the reticle by the predetermined distance. Hence, the particle does not directly form an image on the wafer surface during exposure, but appears as variations in illuminance of the illumination light to decrease errors caused by the particle. 
     FIG. 1  is a schematic view showing the structure of a pellicle. A pellicle  24  is adhered to the pattern surface side of a reticle  23  with an adhesive, or the like, through a reticle support frame  25 . The pellicle  24  is formed of the reticle support frame  25  arranged to surround the circuit pattern on the reticle, and a pellicle film (or pellicle plate)  26  is adhered to one end face of the reticle support frame  25 . The pellicle film  26  has high exposure light transmittance. If the space (to be referred to hereinafter as a pellicle space), surrounded by the pellicle  24  and reticle  23 , is set in a completely sealed state, the pellicle film  26  may inflate or deflate due to the atmospheric pressure difference between the inside and outside of the pellicle space, which is inconvenient. To prevent this, vent holes  27  are formed in the reticle support frame  25  so a pressure difference does not occur between the inside and outside of the pellicle space. Also, dustproof filters (not shown) are provided to prevent an external particle from entering the pellicle space through the vent holes  27 . In the manufacturing process of a semiconductor device, such as an LSI or VLSI, formed of very small patterns, a reduction projection exposure apparatus is used, which reduces and projects a circuit pattern formed on a reticle onto a wafer applied with a resist agent to form a latent image pattern on the resist agent. As the integration density of the semiconductor device increases, a further decrease in the feature size of the circuit pattern is required to lead a need for development of the resist process. Simultaneously, the exposure apparatus is required to have a thinner exposure beam width. 
   Methods of improving the resolution performance of the exposure apparatus include a method of further decreasing an exposure wavelength and a method of increasing the numerical aperture (NA) of a projection optical system. To decrease the exposure wavelength, a KrF excimer laser with an oscillation wavelength of 365-nm i-line to around 248 nm, and an ArF excimer laser with an oscillation wavelength around 193 nm, are used. Recently, exposure using a fluorine (F 2 ) excimer laser with an oscillation wavelength around 157 nm has also been developed. 
   When an ArF excimer laser with a wavelength around far ultraviolet rays, particularly, 193 nm, and a fluorine (F 2 ) excimer laser with an oscillation wavelength around 157 nm are to be used, a problem arises in that a plurality of oxygen (O 2 ) absorption bands are present around their wavelength bands. For this reason, the optical path of an exposure optical system in a projection exposure apparatus, which uses the ArF excimer laser with a wavelength around far ultraviolet rays, particularly, 193 nm, the fluorine (F 2 ) excimer laser with a wavelength around 157 nm, or the like, as a light source, is purged with an inert gas, such as nitrogen. This suppresses the oxygen concentration in the optical path to a low level, on the several ppm order or less. Similarly, moisture (H 2 O) must also be suppressed to a low level, on the several ppm order or less. 
   In order to ensure the transmittance and stability of the fluorine (F 2 ) excimer laser beam in this manner, a reticle stage including a projection lens end face and length measurement interference optical system, and an entire wafer stage, must be arranged in a hermetic chamber, and the interior of the hermetic chamber must be entirely purged with a high-purity inert gas. Also, in order to load and unload a wafer or reticle in and from the hermetic chamber with the inert gas concentration in the hermetic chamber being kept at a constant level, a load-lock chamber is arranged adjacent to the hermetic chamber. Regarding the pellicle space, the illuminance there may be undesirably similarly decreased by light absorption. To prevent this, when unloading a reticle, the pellicle space in the load-lock chamber, or the like, must be purged with an inert gas. 
     FIG. 2  is a schematic view showing an example of a semiconductor exposure apparatus, which uses a fluorine (F 2 ) excimer laser as a light source and has a load-lock mechanism. 
   Referring to  FIG. 2 , a reticle on which a pattern is drawn is loaded on a reticle stage  1 . The pattern on the reticle is transferred onto a wafer in an exposure unit  2 . The exposure unit  2  includes a projection optical system, which projects the reticle pattern onto the wafer, an illumination optical system, which illuminates the reticle, and the like. Illumination light from a fluorine (F 2 ) excimer laser light source (not shown) is guided to the exposure unit  2  through a guide optical system. 
   The reticle stage  1  is covered with a housing  8  and purged with an inert gas. The entire exposure apparatus is covered with an environment chamber  3 . Air controlled to a predetermined temperature circulates in the environment chamber  3  to keep the internal temperature of the environment chamber  3  constant. Clean air, which is temperature-controlled by an air-conditioner  4 , is supplied to the environment chamber  3 . The air-conditioner  4  also has a function of adjusting a predetermined portion, such as an optical system, to an inert gas atmosphere. 
   The housing  8 , which covers the reticle stage  1 , is connected to a reticle load-lock  13 , which is used when loading and unloading the reticle in and from the housing  8 . A reticle hand  15  loads and unloads the reticle and transports the reticle in the housing  8 . A reticle storage  18 , which stores a plurality of reticles, is arranged in the housing  8 . A particle inspection unit  19 , which measures and counts the size and number of particles, such as dust attaching to the reticle surface or pellicle surface, is arranged in the housing  8 . 
   An SMIF (Standard Mechanical InterFace) pod  14 , which stores the reticle, and a reticle relay hand  16 , which transports the reticle between the SMIF pod  14  and the load-lock  13 , are arranged in the environment chamber  3 . After the reticle is loaded in the load-lock  13 , the interior of the load-lock  13  is purged with the inert gas to set it to an inert gas atmosphere identical to that in the housing  8 . Then, the reticle hand  15  transports the reticle to the reticle stage  1 , the reticle stage  18 , or particle inspection unit  19 . 
   An exposure apparatus, which uses an extreme ultraviolet light (EUV light), with a wavelength around 10 nm to 15 nm in the soft X-ray range or an electron beam (EB) is also under development as a next-generation light source. When the wavelength of exposure light decreases to the level of the EUV light or an electron beam, air under the atmospheric pressure no longer transmits the light. Hence, the optical path of the exposure light must be set to a high-vacuum environment of about 10 −4  Pa to 10 −5  PA or more. For this purpose, the reticle stage, including the projection lens end face and length measurement interference optical system, and the entire wafer stage must be arranged in a vacuum chamber, which is more hermetic than the F 2  exposure apparatus. A load-lock chamber must be arranged at a wafer or reticle unloading/loading port. A wafer or reticle must be unloaded or loaded while keeping the vacuum degree in the vacuum chamber. 
   In EUV exposure, a material that transmits EUV light highly efficiently is not available. Hence, a reflection type mask having a pattern surface formed of a multilayered film is used, as disclosed in Japanese Patent Publication No. 7-27198.  FIG. 4  is a schematic view of a reflection type mask used for EUV exposure. A reflection type mask  71  is made of a material having a coefficient of linear thermal expansion of 30 ppb/C.° or less. As the material of the reflection type mask  71 , titanium-doped silica glass, a two-phase glass ceramic material, or the like, can be used. A multilayered film  72  is composed of a reflection layer having a multilayered film structure, such as Mo—Si, and an absorber, which absorbs soft X-rays, and forms an exposure pattern. A conductive film  73  is used to fix the reflection type mask  71  to an electrostatic chuck. 
     FIG. 3  is a view showing an arrangement of a mask stage in a semiconductor exposure apparatus, which uses EUV light as a light source. An EUV exposure stage is arranged above a reduction projection optical system in the exposure apparatus. A mask is held with its upper surface checked, so that a substrate is photosensitized by reflection light. Referring to  FIG. 3 , a reflection type mask stage  81  has an electrostatic mask  82 , which holds the mask  71  by chucking with an electrostatic force during exposure. In a high vacuum atmosphere of about 10 −4  Pa to 10 −5  Pa, serving as an EUV exposure atmosphere, the mask cannot be held by conventional vacuum chucking, and a reticle is held by an electrostatic chuck using the Coulomb force or Johnson-Rahbeck force (to be referred to as the electrostatic force hereinafter), which is generally employed in a vacuum apparatus. In this case, in order to increase the force to hold the reticle, the conductive film  73  may be formed on the chuck holding surface on the mask  71 , as disclosed in Japanese Patent Laid-Open No. 1-152727. Referring to  FIG. 3 , reference numeral  83  denotes a top plate; reference numeral  84 , a linear motor movable element; and reference numeral  85 , linear motor stators, respectively. 
   As described, when the wavelength of exposure light decreases to fall within the EUV range, no material can transmit the light efficiently, and no matter what existing material may be used, EUV light is absorbed undesirably. Accordingly, the conventional method of dust-proofing a reticle by a pellicle cannot be employed. In view of this, a removable pellicle is proposed, which is mounted on a reticle when transporting the reticle and removed from the reticle immediately before exposure. 
   If a removable pellicle is realized using a conventional pellicle, when a load-lock chamber is to be evacuated from the atmospheric pressure to a vacuum state (or vice versa), in order to move the reticle from the atmosphere into a vacuum, the pellicle may be broken by the pressure difference between the inside and outside of the pellicle. Hence, the pellicle must have a strength that can withstand such a pressure difference, or a new dustproof method must be proposed. 
   In order to prevent particles from entering the pellicle space, the pellicle must be fixed to the reticle such that the hermeticity of the pellicle space can be maintained, and must be detachably held so that it can be removed from the reticle easily for exposure. Japanese Patent Laid-Open No. 2002-252162 discloses holding the hermeticity using an O-ring. As the O-ring has adhesion, when it is brought into contact with the reticle, it adheres to the reticle. In this state, when the O-ring is separated from the reticle, dust is produced. The produced dust can attach to the pattern surface of the reticle with the electrostatic force. If the produced dust drops inside the removable pellicle, when the pellicle space is to be vacuum-evacuated or broken in the load-lock chamber, the produced dust may float in the pellicle space to undesirably attach to the pattern surface. 
   Management of only the particles on the pattern surface is not sufficient. When the reticle is fixed to the chuck on the exposure stage, if a particle is sandwiched between the chuck and reticle, it deforms the reticle to distort the pattern surface irregularly, leading to a decrease in exposure performance. It is said that in EUV exposure, with a degradation in accuracy (flatness) of the pattern surface of only about fifty nanometers, the exposure accuracy cannot be satisfied. Accordingly, the particle management on the nanometer order is necessary. In order to solve these problems, a method of decreasing the contact area of the chuck and reticle by using a pin chuck is available. With this method, although the probability of particle sandwiching can be decreased, it cannot be nullified. 
   SUMMARY OF THE INVENTION 
   The present invention has been made based on the recognition of the above problems, and has as its object to provide an exposure apparatus advantageous in using a container that protects one of a reticle and a substrate from a particle, which is formed by a chuck for the one, and which is transported to a stage for holding the chuck. 
   According to a first aspect of the present invention, there is provided a container, for accommodating a substrate, comprising a chuck which chucks and holds the substrate, and a cover which forms a storage space together with the chuck, wherein the substrate is held in the storage space with the cover being mounted on the chuck. 
   According to a preferred embodiment of the present invention, preferably, the container further comprises a port to perform any one of controlling a pressure in the storage space and filling the storage space with an inert gas. 
   According to another preferred embodiment of the present invention, preferably, the chuck has an electrode to electrostatically chuck the substrate and is configured as an electrostatic chuck. 
   According to still another preferred embodiment of the present invention, preferably, the container further comprises a battery to supply power to the electrode. 
   According to still another preferred embodiment of the present invention, preferably, the container further comprises a power supply control circuit, which selectively supplies power provided from any one of the battery and an external device to the electrode. 
   According to still another preferred embodiment of the present invention, preferably, the container further comprises a drop preventive member which prevents the substrate from dropping when the electrode stops electrostatic chucking. 
   According to still another preferred embodiment of the present invention, preferably, the cover is provided with a kinematic coupling mechanism. 
   According to still another preferred embodiment of the present invention, preferably, the chuck has an aligning portion to be aligned on a stage. 
   According to still another preferred embodiment of the present invention, preferably, the container further comprises a seal member which seals the chuck and the cover. 
   According to still another preferred embodiment of the present invention, preferably, the cover has a dustproof wall inside a region where the seal member is arranged. 
   According to still another preferred embodiment of the present invention, preferably, an adhesive material is arranged on an inner surface of the cover. 
   According to still another preferred embodiment of the present invention, preferably, the cover is configured to be capable of destaticizing the mask storage space by an ionizer. 
   According to still another preferred embodiment of the present invention, preferably, the cover includes a portion that transmits destaticizing light so that the storage space can be destaticized by an irradiation ionizer. 
   According to the second aspect of the present invention, there is provided a substrate transporting method of transporting a substrate, comprising steps of transporting, to a stage, a container comprising a chuck, which chucks and holds the substrate, and a cover, which forms a storage space together with the chuck, with the substrate being held in the storage space of the container by the chuck, fixing the chuck to the stage, and separating the cover from the chuck of the container. 
   According to still another preferred embodiment of the present invention, preferably, the cover is fixed to the chuck by setting the storage space to a pressure-reduced state. 
   According to still another preferred embodiment of the present invention, preferably, the chuck is configured as an electrostatic chuck. 
   According to still another preferred embodiment of the present invention, preferably, the method further comprises a step of inspecting a particle on a contact surface between the substrate and the chuck before the substrate is held by the chuck. 
   According to still another preferred embodiment of the present invention, preferably, the method further comprises a step of inspecting any one of a flatness of the substrate and a distortion of a pattern drawn on a mask while the substrate is held by the chuck. 
   According to still another preferred embodiment of the present invention, preferably, the method further comprises a step of destaticizing the storage space. 
   According to still another preferred embodiment of the present invention, preferably, the method further comprises, before a step of fixing the chuck to the stage, a step of performing position adjustment so that positions relative to each other of a reference portion formed on the chuck and a reference portion formed on the substrate fall within a predetermined range. 
   According to the present invention, a substrate, such as a mask or a wafer, can be transported while protecting it from a particle, and use of the substrate after the transportation can be facilitated. 
   More specifically, according to the present invention, a substrate is held by the chuck and transported into a storage space formed of, e.g., the chuck and a cover, so that the substrate can be protected from a particle during the transportation. After the transportation, the cover is separated from the chuck, so that the substrate held by the chuck can be used immediately. 
   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 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
       FIG. 1  is a schematic view showing the structure of a pellicle; 
       FIG. 2  is a schematic view showing an example of a semiconductor exposure apparatus, which uses an F 2  excimer laser as a light source and has a load-lock mechanism; 
       FIG. 3  is a view showing an arrangement of a mask stage in a semiconductor exposure apparatus, which uses EUV light as a light source; 
       FIG. 4  is a schematic view of a reflection type mask used in EUV exposure; 
       FIG. 5  is a sectional view showing the schematic structure of a mask container according to the first embodiment of the present invention; 
       FIG. 6  is a sectional view showing the schematic structure of a mask container according to the second embodiment of the present invention; 
       FIG. 7  is a flowchart showing a mask manipulation procedure (preparation procedure); 
       FIG. 8  is a flowchart showing a mask use procedure (feed procedure); 
       FIG. 9  is a side view showing the entire structure of an EUV exposure apparatus which suitably uses the mask container shown in  FIG. 5 ; 
       FIG. 10  is a plan view showing the entire structure of the EUV exposure apparatus which suitably uses the mask container shown in  FIG. 5 ; 
       FIG. 11A  is a view showing a mask use procedure (feed procedure); 
       FIG. 11B  is a view showing a mask use procedure (feed procedure); 
       FIG. 11C  is a view showing a mask use procedure (feed procedure); 
       FIG. 12  is a sectional view showing the schematic structure of a mask container according to the third embodiment of the present invention; 
       FIG. 13  is a flowchart showing an entire semiconductor device manufacturing process; and 
       FIG. 14  is a flowchart showing the flow of a wafer process in detail. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The preferred embodiments of the present invention will be described with reference to the accompanying drawings. 
   First Embodiment 
     FIG. 5  is a sectional view showing the schematic structure of a mask container according to the first embodiment of the present invention.  FIGS. 9 and 10  are side and plan views, respectively, showing the entire structure of an EUV exposure apparatus, which suitably uses the mask container shown in  FIG. 5 . 
   First, the EUV exposure apparatus will be briefly described with reference to  FIGS. 9 and 10 . A laser device  201 , serving as a light source, has a light-emitting portion  202 . As the laser device, one which excites a gas, such as Xe (xenon) or Sn (tin) to a plasma state to generate light in an EUV wavelength range, is proposed. EUV light generated by the light-emitting portion  202  is guided into the exposure apparatus through an exposure light guide portion  205 . The main body portion of the exposure apparatus is housed in the vacuum chamber  203 . The interior of the vacuum chamber  203  is vacuum-evacuated by a vacuum pump  204  to maintain a high vacuum state. 
   The exposure apparatus incorporates a mask stage  81 , reduction projection optical system  206 , wafer stage  209 , and the like. A reflection type mask  71  formed with an exposure pattern is loaded on the movable portion (top plate) of the mask stage  81 . The reduction projection optical system  206  reduces and projects light, reflected by the mask  71  and includes the exposure pattern, onto a wafer W on the wafer stage  209 . The reduction projection optical system  206  sequentially reflects the light, provided by the mask  71  and includes the exposure pattern, by a plurality of mirrors, to reduce and to project it onto the wafer W with a specified reduction magnification. For example, the wafer stage  209  can align the wafer W in six axes (X-axis, Y-axis, Z-axis, tilt about the X-axis, tilt about the Y-axis, and θ rotation about the Z-axis). 
   The reduction projection mirror optical system  206  is supported on the floor by a projection system support  208 . The mask stage  81  is supported on the floor by a mask stage support  207 . The wafer stage  209  is supported on the floor by a wafer stage support  210 . 
   The reticle stage support  207 , projection system support  208 , and wafer stage support  210  respectively support the reticle stage  81 , reduction projection mirror optical system  206 , and wafer stage  209 , independently of each other. The positions of the reticle stage  81  and reduction projection mirror optical system  206  relative to each other and those of the reduction projection mirror optical system  206  and wafer stage  209  relative to each other are maintained at target relative positions while they are measured by measurement units (not shown). 
   The reticle stage support  207 , projection system support  208 , and wafer stage support  210  are provided with dampers (not shown), which insulate vibration from the floor where the exposure apparatus is installed. 
   A mask transport device  229  and wafer transport device  230  are arranged in a transport system chamber  228 , which is adjacent to the vacuum chamber  203 . The interior of the transport system chamber  228  is set at a pressure slightly higher than that of the atmosphere inside the transport system chamber, typically, higher than that in the clean room atmosphere, so as to prevent a particle from flowing into the transport system chamber  228 . 
   A transport robot  211  arranged in the vacuum chamber  203  supplies the mask  71  to the reticle stage  81  and recovers it from the reticle stage  81 . 
   The space in the transport system chamber  228  is connected to that in the vacuum chamber  203  through a load-lock chamber  214 . The load-lock chamber  214  is connected to the vacuum chamber  203  through a gate valve  212  and to the transport system chamber  228  through a gate valve  213 . The mask is transported between the transport system chamber  228  and vacuum chamber  203  by opening and closing the gate valves  212  and  213 . 
   A container stocker  239 , which stores a mask container  300  exemplified in  FIG. 5 , and a chuck particle inspection unit  242 , which inspects whether or not a particle attaches to a chuck  310  that forms part of the mask container  300 , are also arranged in the transport system chamber  228 . 
   The space in the transport system chamber  228  is also connected to that in the vacuum chamber  203  through a load-lock chamber  224 . The load-lock chamber  224  is connected to the vacuum chamber  203  through a gate valve  222  and to the transport system chamber  228  through a gate valve  223 . The wafer is transported between the transport system chamber  228  and vacuum chamber  203  by opening and closing the gate valves  222  and  223 . 
   A prealignment portion  225  and wafer transport robot  226  are also arranged in the transport system chamber  228 . The prealignment portion  225  measures the outer shape of the wafer W, aligns the wafer W in a θ rotational direction with reference to an orientation flat or notch, and aligns the wafer W in X and Y directions with reference to the wafer center or a predetermined portion of the outer shape of the wafer. The wafer transport robot  226  supplies a wafer, applied with a resist (photosensitive agent) by a coater developer, from an in-line  227  to the prealignment portion  225 , and discharges an exposed wafer to the in-line  227 . The in-line  227  is a transfer station where the wafer is exchanged between the exposure apparatus and the coater developer (not shown), which applies the resist (photosensitive agent) to an unexposed wafer and develops an exposed wafer. 
   The transport chamber  228  is provided with an unloading/loading portion  231 . When an exchange door  232  is opened, a cover  320  and the chuck  310 , which form the container  300 , can be unloaded and loaded between the transport system chamber  228  and the outside. When unloading and loading are not to be performed, the exchange door is closed. 
   In the transport system chamber  228 , a chuck stocker  216 , which can store a plurality of chucks  310  and a cover stocker  240 , which can store a plurality of covers  320 , are arranged above the unloading/loading portion  231 . 
   When the chuck  310  and cover  320  are to be loaded from the outside of the apparatus to the unloading/loading portion  231  and unloaded from the unloading/loading portion  231  to the outside of the apparatus, the chuck  310  and cover  320  are preferably each transported alone, or transported after they are combined to form a container  300  and stored in a dustproof case, or the like. 
   A mask preparation station  233  is arranged in the transport system chamber  228 . At the mask preparation station  233 , the mask  71  is fixed to the chuck  310 . After it is confirmed by the inspection of the mask pattern surface that no particle is sandwiched between the chuck  310  and mask  71  (if a particle is sandwiched, after it is washed off, as will be described later), the cover  320  is attached to the chuck  310 . 
   The mask preparation station  233  preferably has a vacuum evacuation line  233   a  to set a mask storage space (pressure-reduced state), in advance, so as to shorten the time required to send the mask  71  to the vacuum chamber  203  or mask stage  81 . The mask preparation station  233  also preferably has an irradiation ionizer  233   b , such as an ultraviolet irradiation ionizer, which uses EUV light, or the like, or a soft X-ray ionizer, which uses soft X-rays, so as to prevent the mask  71  from being electrically charged by fluid friction during vacuum evacuation. The mask container  300 , which has chucked a mask prepared at the mask preparation station  233 , is transported to a container stocker  239  arranged in the transport system chamber  228  or a container stocker  238  arranged in the vacuum chamber  203  through the load-lock chamber  214 , or sent to the reticle stage  81  directly. The chuck inspection unit  242  can be arranged, e.g., under the container stocker  239 . 
   The mask  71  is loaded into the transport system chamber  228  by an SMIF pod (carrier)  236  from a mask stocker arranged outside the exposure apparatus or another apparatus. As the SMIF pod, for example, a single pod, which can store one mask and a multipod, which can store a plurality of masks, are available. 
   An SMIF indexer  237  is arranged in the transport system chamber  228 . The SMIF indexer  237  has a pod opening/closing mechanism and an elevating mechanism to guide the mask from the SMIF pod  236  set in a load port above the SMIF indexer  237  into the transport system chamber  228 . 
   A mask stocker  235  is also arranged in the transport system chamber  228 . The mask stocker  235  can store a plurality of masks, which are loaded into the transport system chamber  228  by the SMIF pod  236  and SMIF indexer  237 . An inspection unit, which inspects the presence/absence of a particle attaching to the mask, can be arranged above or under the mask stocker  235 . 
   The mask container according to the first embodiment of the present invention will be described with reference to  FIG. 5 . The mask container  300  is a container, which accommodates a reflection mask  71 , and is formed of a chuck  310  and cover  320 . The reflection mask  71  has an exposure pattern formed by, e.g., an Mo—Si multilayered film. 
   The chuck  310  is configured as an electrostatic chuck. The chuck  310  has a support base  82  with a support surface which supports the mask  71  and an electrode  11  arranged in the support base  82 . The reflection mask  71  is held as the electrode  111  is chucked by the support surface of the support base  82  with the electrostatic force generated by the electrode  111 . The chuck  310  has a battery  112  and power supply control circuit  112   a . When power is not externally supplied to the chuck  310  (for example, during transportation), power to hold the reflection mask  71  by electrostatic chucking is supplied from the battery  112  to the electrode  111  through the power supply control circuit  112   a . When power is supplied to the chuck  310  from an external device (for example, a state wherein the mask  71  is mounted on the mask stage  81  or stored in the container stocker  238  or  239 ), power from the external device can be supplied to the electrode  111  through the power supply control circuit  112   a . The mask stage  81  and container stockers  238  and  239  preferably have power supply portions, which supply power to the chuck  310 . 
   The support base  82  of the chuck  310  and the mask  71 , respectively, have marks (not shown) indicating position references. When the mask  71  is to be fixed to the support base  82 , position adjustment is performed such that the relative positional relationship between the two marks falls within a predetermined deviation range. After the fixing, the positional shift amounts of the respective marks are measured. Whether or not the positional shift amounts of the marks fall within an allowable range is checked. Desirably, the positional shift amounts are stored as data. The data can be used as position correction data after the mask  71  is sent to the reticle stage  81  afterward. 
   The cover  20  serves as a dustproof cover, which prevents particles from becoming attached to the mask  71 . The cover  320  is configured to include a cover member  101 . The chuck  310  and cover  320  form the mask storage space  108 , which store the mask  71 . When a seal member  105 , such as an O-ring, is arranged between the chuck  310  and cover  320 , the mask storage space  108  is shielded from the external space. The seal member  105  can be provided to, e.g., the cover member  101 . 
   The cover  320  can include a joint  104  (port) to vacuum-evacuate the mask storage space  108 . When the joint  104  is connected to a vacuum evacuation line (e.g., the vacuum evacuation line  233   a ), the mask storage space  108  can be vacuum-evacuated. During the vacuum evacuation, the pressure difference between the inside and outside of the mask storage space  108  generates an urging force for the cover  320  with respect to the chuck  310  to hold the cover  320 . The joint  104  can be provided to the chuck  310 . The cover  320  can be fixed to the chuck  310  by another lock mechanism. A check valve, which allows gas to shift only from the mask storage space  108  toward the external space, can be arranged between the joint  104  and the mask storage space  108 . Alternatively, a valve that can externally control opening/closing of the mask storage space  108  may be arranged between the joint  104  and the mask storage space  108 . 
   The cover member  101  may be partly or entirely formed of a transparent member (a member which transmits ultraviolet rays or soft X-rays) so that electrification caused by fluid friction during vacuum evacuation is canceled by an irradiation ionizer. 
   The chuck  310  or cover  320  has a valve  113  to cancel the pressure difference between the inside and outside of the mask storage space  108 , so that after the mask  71  is transported to the mask stage  81  in the vacuum chamber  203 , the cover  320  can be separated from the chuck  310 . 
   The cover  320  preferably has a mask drop preventive member  103  serving as a safety measure, so the mask  71  will not drop when the power supply capability from the battery  112  to the electrode  111  decreases (for example, when the output voltage falls below a regulated value). The cover  320  also preferably has kinematic couplings  102  to align the container  300  with the hand of a transport robot, when the container  300 , which houses the mask, is to be transported by the transport robot. While the container  300  is configured as a container to transport a mask substrate, it can be configured as a container to transport a wafer substrate. 
     FIG. 7  is a flowchart showing a manipulation procedure (preparation procedure) for the mask  71 . First, in step  301 , the chuck  310  is transported from the chuck stocker  216  to the chuck particle inspection unit  242 . In step  302 , particle inspection of that surface (the support surface of the support base  82 ) of the chuck  310 , which is to come into contact with the mask  71 , is performed. If the result of the particle inspection is no good (NG), in step  303 , the chuck  310  is unloaded outside of the apparatus via the unloading/loading portion  231 , and cleaned. If the result of the particle inspection is acceptable (OK), the chuck  310  is transported to the mask preparation station  233 . Typically, along with the above steps, in step  311 , the mask  71  is transported from the reticle stocker  235  to the mask particle inspection unit  242 . In step  312 , particle inspection of the two surfaces (i.e., the exposure pattern surface and the contact surface with the chuck  310 ) of the mask  71 , is performed. If the result of the particle inspection is NG, in step  313 , the mask  71  is unloaded outside of the apparatus by using the SMIF pod  236 , and cleaned. If the result of the particle inspection is OK, the mask  71  is transported to the mask preparation station  233 . 
   After it is confirmed that no particle attaches to the chuck  310  or mask  71 , in step  321 , the mask  71  is fixed to the chuck  310 . During the fixing, position adjustment is performed such that the relative positional relationship between the marks formed on the chuck  310  and mask  71  falls within a predetermined deviation range. 
   In step  322 , the flatness of the pattern surface of the mask  71  or the distortion of the pattern drawn on the mask  71  is measured to check whether or not any particle is sandwiched between the chuck  312  and mask  71 . When the measurement value might have an error due to the pattern, a plurality of flatness measurement regions may be formed in the pattern region or on the scribe line, and particle measurement may be performed in the measurement regions. Alternatively, an arbitrary mark may be formed in the pattern, and the presence/absence of the particle may be checked from the distortion of the mark. If the inspection result is NG, the chuck  312  and mask  71  are returned to steps  302  and  312 , and particle inspection is performed again. 
   If the inspection result is OK, in step  323 , the cover  320  is extracted from the cover stocker  240  and mounted on the chuck  310 . In step  324 , the vacuum evacuation line  233   a  is connected to the joint  104 , and the mask storage space  108  is vacuum-evacuated. In this case, the pressure difference between the inside and outside of the mask storage space  108  urges the cover  320  and chuck  310  against each other, to fix the cover  320  to the chuck  310 . This forms the container  300 , which accommodates the mask  71 . The pressure in the mask storage space  108  is preferably set to be lower than that in the vacuum chamber  203 , so that when the container  300  is loaded in the vacuum chamber  203 , the chuck  310  and cover  320  will not separate from each other. 
   In step  325 , the container  300 , which accommodates the mask  71 , is transported to the container stocker  239  in the transport system chamber  228 , or to the container stocker  238  in the vacuum chamber  203  through the load-lock chamber  214 . The container  300  is then put in the container stocker  239  or  238  and set in a storage standby state. 
   The use procedure for the mask  71  will be described with reference to  FIG. 8  and  FIGS. 11A to 11C . 
   As exemplified in  FIGS. 11A to 11C , the reticle stage  81  has a top plate  83 , linear motor movable elements  84  fixed to the top plate  83 , linear motor stators  85  supported by the mask stage support  207  ( FIG. 9 ), and aligning pins (engaging portions)  86  formed on the top plate  83 . 
   The container  300 , in which the mask  71  is held in the mask storage space  108  by the chuck  310 , has aligning holes (engaging portions)  82   a  in the support base  82 . When the aligning pins  86  are fitted in the aligning holes  82   a , the container  300  (chuck  310 ) is aligned on the top plate  83  of the mask stage  81 . The container  300  is manipulated by a transport hand  121  attached to the arm of the transport robot  211  ( FIGS. 9 and 10 ). Kinematic coupling pins  122  are formed on the transport hand  121  and engage with the kinematic couplings  102  provided to the lower surface of a cover member  110  of the cover  320  so as to align the container  300  (accordingly, the chuck  310  and the mask  71  held by it) with the transport hand  121 . 
     FIG. 11A  shows a state wherein the container  300  is transported to below the reticle stage  81  by the transport robot  211 .  FIG. 11B  shows a state wherein the transport hand  121  of the transport robot  211  moves upward to align and to fix the support base  82  of the chuck  310  on the top plate  83 . In this state, the power supply terminal of the chuck  310  is connected to that of the top plate  83 , and power is supplied from the top plate  83  to the clamp electrode  111  through the power supply control circuit  112   a  of the chuck  310 . 
   Then, the valve  113  is opened to cancel the pressure difference between the inside and the outside of the mask storage space  108 , and the cover  320  is removed from the chuck  310 .  FIG. 11C  shows a state wherein the cover  320  is removed from the chuck  310 . When removing the cover  320  from the chuck  310 , the cover  320  may be adhered to the chuck  310  by the seal member  105 , such as an O-ring. Therefore, preferably, a clamp mechanism, which clamps the cover  320 , is provided on the transport hand  121 , or the kinematic coupling pins  122  are replaced by collet kinematic clamps, which use vacuum chucking. 
   A description will be made with reference to  FIG. 8 . First, in step  33 , the mask  71 , which is stored with its cleanliness being guaranteed in advance, is extracted from the chuck stocker  239  or  238  as it is accommodated in the container  300 . When the container  300  is to be extracted from the container stocker  239 , it is guided into the vacuum chamber  203  through the load-lock chamber  214 . 
   In step  332 , the mask  71 , accommodated in the container  300 , is transported to the exposure stage. In step  333 , the chuck  310 , which forms part of the container  300 , is fixed to the top plate  83 . In this case, even if a particle is sandwiched between the chuck  310  and top plate  83 , it will not largely influence the flatness of the pattern surface or the distortion of the pattern of the mask  71 , because the chuck  310  is sufficiently rigid. 
   In step  334 , the valve  113  is opened and the cover  320  is removed from the chuck  310 . In step  335 , the cover  320  is unloaded. In step  336 , the positional shift amount between the reference mark on the chuck  310  and the reference mark on the wafer stage  209  is measured. In step  337 , exposure is performed using both the value measured in step  336  and the positional shift amount of the reference mark between the chuck and mask, which is measured in step  321 , as data for position correction of the mask and wafer. 
   Although the description is made on the assumption that the transport robot  211  is of the single hand type, to perform mask exchange on the reticle stage efficiently, it is preferable to employ a double hand type transport robot. 
   In this manner, when the surface accuracy of the exposure pattern surface is guaranteed in the previous step, and the mask  71  is transported with the cover attached until immediately before exposure, highly reliable particle management can be performed. 
   The mask preparation described in  FIG. 7  need not always be performed in the exposure apparatus. A mask stocker in the factory may be provided with a similar mask preparation facility. The mask may be fixed to the chuck, and a cover may be attached to the chuck. Then, the mask may be supplied to the exposure apparatus. 
   An application to the vacuum exposure apparatus has been described as one embodiment of the present invention. When the present invention is to be applied to fluorine (F 2 ) excimer laser exposure, the mask storage space  108  may be purged with an inert gas. In this case, the inert gas fills the mask storage space  108  through the joint  104 . 
   Second Embodiment 
     FIG. 6  is a sectional view showing the schematic structure of a mask container according to the second embodiment of the present invention. Portions that are common to the first embodiment are denoted by the same reference numerals. A mask container  300  according to the second embodiment is provided with a dustproof wall  106 . This prevents a particle produced by an O-ring  105  from dropping inside a cover  320  when the cover  320  is to be removed after the mask container  300  is supplied to a reticle stage. If a plurality of dustproof walls  106  are provided to both the cover  320  and a chuck  310  to form a labyrinth, the dustproof performance may be improved. 
   In case a particle should attach to the inside of a cover member  101 , when a mask storage space  108  is vacuum-evacuated, the particle may float in the mask storage space  108  and attach to the mask. In order to prevent this, an adhesive  107  may be applied to the inner surface of the cover member  101  of the chuck  310  to trap the particle. As the adhesive  107 , a fluorine-based adhesive, which produces a small amount of gas, is suitable. 
   Third Embodiment 
   The present invention has a dustproof effect, not only for transportation in a vacuum or inert purge atmosphere, but also for transportation in the ordinary atmosphere.  FIG. 12  is a sectional view showing the schematic structure of a mask container according to the third embodiment of the present invention. The mask container of the third embodiment is an application to transportation in the atmosphere. 
   A mask container  400  according to the third embodiment is a container which accommodates a mask  71 , and is formed of a chuck  410  and cover  420 . The cover  420  has mask retainers  114 , which hold the mask  7   y   1  by urging it against a support base  82  of the chuck  410 . For example, the mask retainers  114  can be made of an elastic body, such as rubber. The cover  420  is fixed to the chuck  410  by lock levers (lock mechanisms)  115 . For example, the lock levers  115  are configured to respectively pivot about rotating shafts  116  provided as fulcrums to the chuck  410 . When transporting the mask  71  by holding it by the mask retainers  114 , and fixing the chuck to a stage  1 , the mask  71  is fixed to the chuck by vacuum chucking. In this case, a position reference mark on the mask may be measured and used as correction data of the stage drive target position. Alternatively, before fixing the mask to the chuck by vacuum chucking, position adjustment may be performed, such that the reference mark on the mask falls within a predetermined deviation range with respect to the position reference of the chuck, and, after that, the mask may be fixed to the chuck. A reticle stage for exposure with ultraviolet rays, such as i-line or a KrF, an ArF, or a fluorine (F 2 ) excimer laser is usually formed, such that a chuck and EUV stage are inverted upside down. Thus, for transportation as well, the mask container  400  may be transported, such that it is inverted upside down from the state shown in  FIG. 12 . 
   [Application] 
   A semiconductor device manufacturing process using the exposure apparatus described above will be described.  FIG. 13  is a flowchart showing the flow of an entire semiconductor device manufacturing process. In step S 1  (circuit design), the circuit of a semiconductor device is designed. In step S 2  (mask fabrication), a mask is fabricated on the basis of the designed circuit pattern. In step S 3  (wafer manufacture), a wafer is manufactured using a material such as silicon. In step S 4  (wafer process), called a preprocess, an actual circuit is formed on the wafer in accordance with lithography using the mask and wafer described above. In the next step, step S 5  (assembly), called a post-process, a semiconductor chip is formed from the wafer fabricated in step S 4 . This step includes processes such as assembly (dicing and bonding) and packing (chip encapsulation). In step S 6  (inspection), inspections, such as an operation check test and a durability test, of the semiconductor device fabricated in step S 5 , are performed. A semiconductor device is finished with these steps and shipped (step S 7 ). 
     FIG. 14  is a flowchart showing the flow of the above wafer process in detail. In step S 11  (oxidation), the surface of the wafer is oxidized. In step S 12  (CVD), an insulating film is formed on the wafer surface. In step S 13  (electrode formation), an electrode is formed on the wafer by deposition. In step S 14  (ion implantation), ions are implanted in the wafer. In step S 15  (resist process), a photosensitive agent is applied to the wafer. In step S 16  (exposure), the circuit pattern is transferred to the wafer applied with the photosensitive agent by the exposure apparatus described above to form a latent image pattern. A substrate as a mask or a substrate as a wafer is transported in accordance with the method described above. In step S 17  (development), the latent image pattern transferred to the wafer is developed to form a resist pattern. In step S 18  (etching), portions other than the developed resist image are removed. In step S 19  (resist removal), any unnecessary resist after etching is removed. These steps are repeated to form multiple circuit patterns on the wafer. 
   [Utility] 
   As has been described above, according to the respective embodiments, a substrate, such as a mask or wafer, can be transported, while protecting it from a particle, and use of the substrate after transportation can be facilitated. 
   More specifically, the substrate is transported as it is held in a storage space, formed of a chuck and cover, by the chuck. Thus, the substrate can be protected from the particle during transportation. After the transportation, the cover is removed from the chuck. Thus, the substrate held by the chuck can be used immediately. 
   While the substrate is fixed to the chuck, it is checked that the surface accuracy of the substrate falls within an allowable range. The cover is fixed to the chuck to form a container, which is to accommodate the substrate. The substrate is transported as it is accommodated in the container. After that, the cover is separated from the chuck, and the substrate held by the chuck is used or processed. Thus, the substrate can be used or processed within a short period of time while preventing any particle from attaching to the substrate. For example, assume that this container is to be applied for transportation of a mask. In this case, a mask may be prepared, such that its surface accuracy and particle attaching are guaranteed to fall within allowable ranges. When necessary, the mask can be accommodated in the container and provided to a mask stage quickly. 
   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.