Exposure method and projection exposure apparatus

Abstract

A projection exposure apparatus carries out scan exposure with illumination flux of slit(s) by moving a mask and a substrate in a direction of one-dimension at synchronized speeds with each other. The mask is inclined with a predetermined angle relative to the substrate in the direction of one-dimensional movement. The substrate is also moved in a direction of optical axis of projection optical system when moved in the direction of one-dimension, such that a central part of transfer area on the substrate is located on a best focal plane of projection optical system upon scan exposure.

What is claimed is:  
     
       1. A method for exposure in which a pattern formed in a transfer region on a mask is subject to projection exposure through a projection optical system to be led onto an area to be exposed on a photosensitive substrate, and said mask and photosensitive substrate are at least one-dimensionally, relatively scanned with respect to a projection field of said projection optical system: comprising, 
       limiting a width of said area of pattern image projected on said photosensitive substrate through the projection optical system to an approximately constant value in a direction of one-dimensional scan; and  
       inclining a local surface on said photosensitive substrate on which said pattern image is formed, relative to a best focal plane of said projection optical system in the direction of one-dimensional scan.  
     
     
       2. A method for exposure according to claim  1 , wherein a central part of said local surface in the direction of one-dimensional scan on said photosensitive substrate, on which said pattern image is formed, substantially coincides with said best focal plane of projection optical system when scanned for exposure. 
     
     
       3. A method for exposure according to claim  1 , wherein, defining a width of local surface on the photosensitive substrate in the direction of one-dimensional scan, on which said pattern image is formed as D ap , an angle of inclination between said local surface and said best focal plane as θ 1 , and a depth of focus of said projection optical system in a direction of optical axis as ΔZ f , the following relation is satisfied by adjusting at least one of said width D ap  of the pattern image area and said inclination angle θ 1 ; 
       
         
           D ap ·sin θ 1 ≧Z f .  
         
       
     
     
       4. A method for exposure according to claim  1 , wherein, the order to limit said width of pattern image area in the direction of one-dimensional scan, a shape of illumination flux for exposure is made rectangular on said mask to be illuminated thereby, and an intensity distribution of said rectangular illumination flux has at least two peaks in the direction of one-dimensional scan. 
     
     
       5. A projection exposure apparatus comprising: 
       a projection optical system for projecting a pattern formed in a transfer region on a mask, onto an area to be exposed on a photosensitive substrate;  
       a mask stage for one-dimensionally moving said mask over a region beyond a width of said transfer region in a direction of movement;  
       a substrate stage for one-dimensionally moving said photosensitive substrate in the direction of one-dimensional movement of said mask stage at a speed synchronized with a movement speed of said mask stage;  
       illumination means for illuminating said mask with an illumination flux for exposure, having a shape between a rectangle and a slit within the projection field of said projection optical system and having an approximately constant width in the direction of one-dimensional movement;  
       a substrate holder the holding said photosensitive substrate on said substrate stage with a predetermined inclination angle with respect to the direction of one-dimensional movement of illuminated area formed by said illumination flux on said photosensitive substrate through said mask and said projection optical system;  
       holder drive means for moving said substrate holder in a direction of optical axis of said projection optical system such that a central part of said illuminated area on said photosensitive substrate is located near a best focal plane of said projection optical system; and  
       control means for controlling said holder drive means to maintain an imaging condition of pattern image of said mask on said photosensitive substrate with correspondence to a position in said illuminated area in the direction of one-dimensional movement while scan exposure of pattern of said mask is effected on said area to be exposed.  
     
     
       6. A scanning exposure apparatus for exposing a shot area defined by street lines on a sensitive surface of a substrate with an image of a pattern of a mask, said apparatus comprising: 
       
         a projection lens having a circular image field to project an image of the pattern of the mask onto the shot area of the substrate;  
       
         a scanning mechanism for one - dimensionally, relatively scanning the mask and substrate with respect to the circular image field of said projection lens at a predetermined velocity ratio corresponding to a magnification of said projection lens in order to perform scanning exposure of said shot area;    
         an illumination system for irradiating the mask with radiation having a rectangular distribution which is elongated in a cross - direction of said one - dimensional scan direction and is arranged at a center of a circular object field of said projection lens; and    
       
         an adjusting mechanism for adjusting the length of the rectangular distribution of said radiation in accordance with positions of said street lines.  
       
     
     
       7. A scanning exposure apparatus for exposing an image of a pattern of a mask onto a shot area defined on a sensitive substrate, said apparatus comprising: 
       
         a double telecentric reduction optical system having a circular image field and being composed only of refraction elements or of a combination of refraction and reflection elements, to project an image of the pattern of the mask onto the shot area of the substrate;  
       
         a scanning mechanism for one - dimensionally, relatively scanning the mask and substrate with respect to the circular image field of said reduction optical system at a predetermined velocity ratio corresponding to a magnification of said reduction optical system;    
         an illumination optical system for irradiating the mask with radiation having a rectangular distribution which is elongated perpendicularly to said one - dimensional scan direction and is arranged at a center of a circular object field of said reduction optical system, during the operation of said scanning mechanism; and    
       
         a variable aperture mechanism for adjusting the length of the rectangular distribution of said radiation in accordance with the size of said shot area;  
       
       
         wherein different portions of said shot area are successively scanned by rectangular pattern image portions of the mask.  
       
     
     
       8. A scanning exposure apparatus for exposing a predetermined region of a sensitive surface of a plate with an image of a pattern of a mask, said apparatus comprising: 
       ( a )  a double telecentric projection lens for projecting an image of the pattern of the mask onto the region of the plate;    
       ( b )  a scanning mechanism for one - dimensionally, relatively scanning the mask and plate with respect to a circular image field of said projection lens at a predetermined velocity ratio in order to perform scanning exposure of the region of said plate;    
       ( c )  an illumination system for irradiating the mask with radiation having a rectangular shape which is elongated in a cross - direction of the one - dimensional scanning direction and is arranged at the center of a circular object field of said projection lens, whereby a rectangular image portion of the mask pattern is projected toward the plate through said projection lens; and    
       ( d )  a focus condition detector for detecting a focus deviation of the surface of said plate relative to a best imaging plane of said projection lens within an area corresponding to said rectangular image portion, during the scanning of said scanning mechanism.    
     
     
       9. An apparatus according to claim  8 , wherein said illuminating system includes an adjusting mechanism for adjusting the length of said rectangular shape according to the size of said region on said plate.  
     
     
       10. A scanning exposure method in which an image of a pattern of a mask is projected onto a shot area of a photosensitive plate through a projection system, and the mask and plate are at least one- dimensionally, relatively scanned with respect to a field of said projection system, the method comprising the steps of:    
       ( a )  providing a telecentric projection system having a circular image field which is smaller than said shot area and an optical axis which passes through the center of said circular image field;    
       ( b )  limiting an effective imaging area in said circular image field to a diametrically extending rectangular region having a predetermined width in said one - dimensional scan direction and having a predetermined length in a cross - direction of said one - dimensional scan direction,    
         wherein the middle of said width is arranged substantially at the center of said circular image field and said length is adjusted substantially in coincidence with a size of said shot area along said cross - direction; and    
       ( c )  scanning the mask and the plate relative to said rectangular effective image area in the one - dimensional scan direction with a predetermined velocity ratio in order to successively expose different portions of said shot area with rectangular pattern image portions of the mask.    
     
     
       11. A method for scanning exposure in which a pattern region of a mask is projected onto a shot area of a photosensitive plate through a projection system, and the mask and plate are at least one- dimensionally, relatively scanned with respect to a field of said projection system, the method comprising the steps of:    
       ( a )  providing a double telecentric projection lens having a circular image field which is smaller than said shot area and an optical axis which passes through the center of said circular image field;    
       ( b )  limiting an effective imaging area in the circular image field to an approximately rectangular shape having a predetermined width in the one - dimensional scan direction and having a predetermined length in a crossing direction of the one dimensional scan direction,    
       
         wherein the middle of said width is arranged substantially at the center of said circular image field;  
       
       ( c )  scanning the mask and plate relative to said rectangular effective imaging area in the one - dimensional scan direction with a predetermined velocity ratio in order to expose said shot area with an image of the pattern region of the mask;    
       ( d )  optically detecting a position of a surface portion of said plate, corresponding to said rectangular effective imaging area on the plate, along said optical axis during said scanning; and    
       ( e )  correcting focusing error between said surface portion of the plate and a best imaging plane of said projection lens in response to said position detecting during said scanning.    
     
     
       12. A method according to claim  11 , wherein said limiting of the effective imaging area is performed by controlling a distribution shape of radiation irradiating the mask.  
     
     
       13. A method for scanning exposure in which a pattern region of a mask is projected onto a shot area of a photosensitive plate through a projection system, and the mask and plate are at least one- dimensionally, relatively scanned with respect to a field of said projection system, the method comprising the steps of:    
       ( a )  providing a reduction imaging lens having a circular image field which is smaller than said shot area and an optical axis which passes through the center of said circular image field;    
       ( b )  limiting a shape of an effective imaging area in the circular image field to a diametrically extending rectangular region having a predetermined width in the one - dimensional scan direction and having a predetermined length in a cross - direction of the one - dimensional scan direction,    
         wherein the middle of said width is arranged substantially at the center of said circular image field and said length is adjusted substantially in coincidence with a size of said shot area along said cross - direction;    
       ( c )  scanning the mask and plate relative to said rectangular effective imaging area in the one - dimensional scan direction with a predetermined velocity ratio in order to expose said shot area with an image of the pattern region of the mask;    
       ( d )  optically detecting a focusing deviation and a leveling deviation of a surface portion of the plate corresponding to said rectangular effective imaging area on the plate, during said scanning; and    
       ( e )  adjusting focusing and leveling conditions between said surface portion of the plate and a best imaging plane of said reduction imaging lens in response to said focusing and leveling deviations, respectively, during said scanning.