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 in which a substrate is exposed with an energy beam by moving a mask and the substrate relative to the energy beam, comprising: 
       
         a projection system, arranged in a path of the energy beam, which is a reduction system to project a reduction image of a pattern formed on the mask onto the substrate, an image field of the projection system being a circular image field;  
       
         an illumination system, disposed along the path of the energy beam, which distributes the energy beam within a specified slit - shaped region in the image field of the projection system;    
       
         a first stage, disposed on an object surface side of the projection system, which is movable in a first direction while holding the mask during scanning exposure of the substrate;  
       
       
         a first interferometer which measures positional information of the first stage in the first direction during the scanning exposure;  
       
       
         a second stage, disposed on an image surface side of the projection system, which is movable in a second direction while holding the substrate during the scanning exposure, wherein the specified region is a substantially rectangular region which diametrically extends within the circular image field in a direction substantially perpendicular to the second direction and wherein a width of the specified region in the second direction is shorter than a length of the specified region in a direction perpendicular to the second direction;  
       
       
         a second interferometer, which measures positional information of the second stage in the second direction during the scanning exposure;  
       
       
         a driving unit connected to the first and second interferometers to adjust a relative relationship between the mask and the substrate based on the positional information measured by the first and second interferometers during the exposure, said driving unit including a first driving system to move the first stage and a second driving system to move the second stage, wherein the first stage is moved at a first speed and the second stage is moved at a second speed which is different from the first speed and a ratio between the first speed and the second speed is determined in accordance with a reduction magnification of the projection system;  
       
       
         a detection unit disposed apart from the second stage to detect inclination information of the substrate during the scanning exposure, said detection unit including a projecting element to project a detection light onto the substrate within the specified region and a receiving element to receive the detection light reflected on the substrate; and  
       
       
         an adjustment system, connected to the detection unit, which controls inclination of the substrate during the scanning exposure to adjust a relative inclination between the substrate and an image surface of the projection system in the specified region based on the information detected by the detection unit. 
       
     
     
       7. An apparatus according to  claim 6 , wherein: 
       
         the adjustment system controls the inclination of the substrate by moving the substrate at three points. 
       
     
     
       8. An apparatus according to  claim 6 , wherein: 
       
         the adjustment system controls the inclination of the substrate so that the substrate substantially coincides with an image surface of the projection system at a center of the specified region. 
       
     
     
       9. An apparatus according to  claim 6 , wherein: 
       
         the first interferometer measures rotational information of the first stage during the scanning exposure. 
       
     
     
       10. An apparatus according to  claim 9 , wherein: 
       
         the rotational information includes yawing information. 
       
     
     
       11. An apparatus according to  claim 9 , further comprising: 
       
         a reflection member, disposed in the path of the energy beam, which reflects the energy beam, wherein the second direction is substantially parallel to a plane which includes an axis of the energy beam incident on the reflection member and an axis of the energy beam reflected by the reflection member. 
       
     
     
       12. An apparatus according to  claim 6 , wherein: 
       
         the second interferometer measures rotational information of the second stage during the scanning exposure. 
       
     
     
       13. An apparatus according to  claim 6 , further comprising: 
       
         a first reference reflection surface for the measurement of the first interferometer, arranged on a barrel of the projection system; and  
       
       
         a second reference reflection surface for the measurement of the second interferometer, arranged on the barrel of the projection system. 
       
     
     
       14. An apparatus according to  claim 6 , further comprising: 
       
         a reference member, disposed on the second stage, which defines a relationship between the positional information measured by the first interferometer and the positional information measured by the second interferometer. 
       
     
     
       15. An apparatus according to  claim 6 , wherein: 
       
         speed information of the first and second stages is detected during the scanning exposure. 
       
     
     
       16. An apparatus according to  claim 6 , further comprising: 
       
         a reflection member, disposed in the path of the energy beam, which reflects the energy beam, wherein the second direction is substantially parallel to a plane which includes an axis of the energy beam incident on the reflection member and an axis of the energy beam reflected by the reflection member. 
       
     
     
       17. An apparatus according to  claim 6 , wherein: 
       
         the projection system is composed only of refraction elements, and wherein an optical axis of the projection system is substantially in one straight line. 
       
     
     
       18. An apparatus according to  claim 17 , wherein: 
       
         the projection system is telecentric on the image surface side and on the object surface side. 
       
     
     
       19. A scanning exposure method in which a substrate is exposed with an energy beam, comprising: 
       
         moving a mask in a first direction relative to the energy beam during scanning exposure;  
       
       
         moving a substrate in a second direction relative to the energy beam during the scanning exposure, wherein the mask is moved at a first speed and the substrate is moved at a second speed which is different from the first speed, and a ratio between the first speed and the second speed is determined in accordance with a reduction magnification of a projection system;  
       
       
         distributing the energy beam within a specified rectangular region in a circular image field of the projection system during the scanning exposure, wherein a width of the specified region in the second direction is shorter than a length of the specified region in a direction perpendicular to the second direction;  
       
       
         measuring positional information of the mask by using a first interferometer system during the scanning exposure;  
       
       
         measuring positional information of the substrate by using a second interferometer system during the scanning exposure;  
       
       
         adjusting a relative relationship between the mask and the substrate based on the positional information measured by the first and second interferometer systems during the scanning exposure;  
       
       
         detecting, during the scanning exposure, inclination information of the substrate by projecting detecting light within the specified region onto the substrate; and  
       
       
         controlling inclination of the substrate during the scanning exposure to adjust a relative inclination between the substrate and an image surface of the projection system in the specified region based on the detected inclination information. 
       
     
     
       20. A method according to  claim 19 , further comprising: 
       
         measuring rotational information of the mask by using the first interferometer system; and  
       
       
         measuring rotational information of the substrate by using the second interferometer system. 
       
     
     
       21. A method according to  claim 20 , wherein the inclination of the substrate is controlled so that the substrate substantially coincides the image surface of the projection system at a center of the specified region. 
     
     
       22. A method according to  claim 21 , further comprising: 
       
         detecting speed information of the mask and the substrate during the scanning exposure.