Patent Number: 
Section: claims

1. A lithographic projection apparatus constructed and arranged to scan-image a mask pattern in a mask onto a substrate with a radiation sensitive layer, the mask having at least one transmissive region bounded at least in the scan direction by opaque regions, the lithographic projection apparatus comprising: a radiation system comprising a radiation source and an illumination system, said radiation system generating an illumination beam and controlling said illumination beam to scan said transmissive region between said opaque regions, said illumination beam comprising charged particles;  a first movable object table provided with a mask holder constructed and arranged to hold a mask;  a second movable object table provided with a substrate holder constructed and arranged to hold a substrate; and  a projection system constructed and arranged to image an irradiated portion of the mask onto a target portion of the substrate;  wherein said illumination system is embodied to begin a scan by generating a relatively narrow beam adjacent one of said opaque regions, to increase the width of said beam whilst it remains adjacent said opaque region, and to scan said beam towards the other of said opaque regions, thereby to provide a substantially uniform exposure on the substrate. 2. An apparatus according to  claim 1 , wherein said illumination system is embodied at the end of the scan, when said beam approaches said other opaque region, to reduce the width of said beam whilst said beam is adjacent said other opaque region. claim 1 3. An apparatus according to  claim 1 , wherein said illumination system is embodied substantially to avoid illuminating said opaque regions. claim 1 4. An apparatus according to  claim 1 , wherein said illumination system is embodied such that the change n the width of said beam is performed substantially linearly at a rate equal to a speed at which said transmissive region is scanned. claim 1 5. An apparatus according to  claim 1 , wherein said mask comprises a reticle divided into a plurality of elongate sub-fields separated by struts, said transmissive region comprising said sub-fields and said opaque regions comprising said struts. claim 1 6. An apparatus according to  claim 5 , wherein said illumination system is embodied to scan along the length of said sub-fields and said apparatus further comprises a transverse scanning unit constructed and arranged to scan said mask and said substrate perpendicularly to said sub-fields. claim 5 7. An apparatus according to  claim 6 , wherein said illumination system is embodied to scan the length of a sub-field a plurality of times between operations of said transverse scanning unit. claim 6 8. An apparatus according to  claim 1 , wherein said illumination system comprises first and second shaping apertures and a first deflection unit constructed and arranged to displace said image of said first shaping aperture, thereby controlling the width of said illumination beam. claim 1 9. An apparatus according to  claim 8 , wherein said illumination system further comprises a second deflection unit constructed and arranged to displace said illumination beam on said mask. claim 8 10. An apparatus according to  claim 8 , wherein said illumination system further comprises a first focusing unit constructed and arranged to project an image of said first shaping aperture onto the plane of said second shaping aperture. claim 8 11. An apparatus according to  claim 1 , wherein the projection system includes a projection focusing unit controlled in accordance with the width of or current in said projection beam. claim 1 12. An apparatus according to  claim 1 , wherein said illumination beam has a hexagonal cross-section at the mask, and said illumination system is embodied to vary the width of said illumination beam parallel to said scan direction. claim 1 13. A method of manufacturing a device using a lithographic projection apparatus comprising: a radiation system comprising a radiation source and an illumination system, said radiation system generating an illumination beam, said illumination beam comprising charged particles;  a first object table provided with a mask holder constructed and arranged to hold a mask;  a second object table provided with a substrate holder constructed and arranged to hold a substrate; and  a projection system constructed and arranged to image an irradiated portion of the mask onto a target portion of the substrate provided with a radiation sensitive layer; the method comprising:  scan-imaging a mask pattern in said mask onto said target portion of said substrate, the having at least one transmissive region bounded at least in the scan direction by opaque regions,  wherein said imaging comprises:  at the beginning of a scan, generating a relatively narrow beam adjacent one of said opaque regions, increasing the width of said beam while it remains adjacent said opaque region, and scanning said beam towards the other of said opaque regions, thereby to provide a substantially uniform exposure on the substrate. 14. A device manufactured using a lithographic projection apparatus comprising: a radiation system comprising a radiation source and an illumination system, said radiation system generating an illumination beam comprising charged particles;  a first object table provided with a mask holder constructed and arranged to hold a mask;  a second object table provided with a substrate holder constructed and arranged to hold a substrate; and  a projection system constructed and arranged to image an irradiated portion of the mask onto a target portion of the substrate provided with a radiation sensitive layer; the method comprising:  scan-imaging a mask pattern in said mask onto said target portion of said substrate, the mask having at least one transmissive region bounded at least in a scan direction by opaque regions,  wherein said imaging comprises at the beginning of a scan, generating a relatively narrow beam adjacent one of said opaque regions, increasing a width of said beam whilst it remains adjacent said opaque region, and scanning said beam towards the other of said opaque regions, thereby to provide a substantially uniform exposure on the substrate.