Method of forming pattern and projection aligner for carrying out the same

Abstract

An area on a photoresist film which is formed on a substrate surface having a topography, is exposed a plurality of times in such a manner that the image plane of a mask pattern is formed at a plurality of positions which are spaced apart from a reference plane in the substrate in the direction of an optical axis, and then the photoresist film is developed to form a resist pattern. According to the above method, the effective focal depth of the projection aligner used is enhanced, and moreover the reduction of the image contrast at the photoresist film is very small by the plural exposure operations. Accordingly, a fine pattern can be formed accurately on the substrate surface having the topography.

We claim: 
     
       1. A reduction projection aligner comprising: first means for holding a mask having a predetermined mask pattern;   an exposure shutter;   second means for controlling said exposure shutter;   a stage for holding a substrate on which a pattern is to be formed;   third means for positioning said substrate at predetermined plural positions;   an optical system for projecting said mask pattern on said substrate;   fourth means for storing the number of image planes or said mask pattern, the positions of each said image planes on an optical axis of said optical system and the quantity of light incident on each image plane; and   fifth means for controlling said second and third means such that a plurality of said image planes of said mask pattern are formed on said substrate spaced from each other in the direction of said optical axis.   
     
     
       2. A reduction projection aligner according to claim 1, wherein said third means includes means for moving said stage in the direction of said optical axis. 
     
     
       3. A reduction projection aligner according to claim 1, wherein said third means comprises means for moving said stage in directions defined in a plane perpendicular to said optical axis. 
     
     
       4. A reduction projection aligner according to claim 1, wherein said light comprises ultraviolet rays. 
     
     
       5. A reduction projection aligner according to claim 4, wherein said ultraviolet light is selected from the group consisting of i-line and g-line. 
     
     
       6. A reduction projection aligner according to claim 1, wherein said light is emitted from an excimer laser. 
     
     
       7. A reduction projection aligner comprising: first means for holding a mask having a predetermined mask pattern;   a stage for holding a substrate on which a pattern is to be formed;   an exposure shutter;   an optical system for projecting said mask pattern on said substrate;   second means for moving said stage in a direction of an optical axis of said optical system;   third means for moving said stage in the directions defined by a plane perpendicular to said optical axis;   fourth means for controlling said exposure shutter; and   fifth means for controlling said second and fourth means such that said substrate is successively positioned at predetermined plural positions spaced from each other in the direction of said optical axis and said substrate is subjected to a light exposure operation at each of said plural positions.   
     
     
       8. A reduction projection aligner according to claim 7, wherein said light comprises ultraviolet rays. 
     
     
       9. A reduction projection aligner according to claim 8, wherein said ultraviolet rays is selected from the group consisting of i-line and g-line. 
     
     
       10. A reduction projection aligner according to claim 7, wherein said light is emitted from an excimer laser. 
     
     
       11. A reduction projection aligner, comprising: means for holding a mask having a predetermined mask pattern;   a stage for holding a substrate, on which a pattern is to be formed; an optical system for projecting said mask pattern on the substrate; and   means for forming an image plane of the mask pattern at plural positions spaced apart from each other in the direction of the optical axis of said optical system, to perform an exposure operation in such a manner that the image plane of the mask pattern is formed at said plural positions.   
     
     
       12. A reduction projection aligner according to claim 11, wherein said means for forming the image plane of said mask pattern at the plural positions includes means for moving the substrate in the direction of the optical axis, to perform the exposure operation a plurality of times in such a manner that the image plane of said mask pattern is formed at a plurality of positions spaced apart from each other in the direction of the optical axis. 
     
     
       13. A reduction projection aligner according to claim 11, wherein said means for forming the image planes of said mask pattern at the plural positions includes means for moving a lens of said optical system or said mask. .Iadd. 
     
     
       14.  A reduction projection aligner comprising: means for holding a mask having a predetermined mask pattern;   a stage for holding a substrate on which a pattern is to be formed;   an optical system for projecting said mask pattern onto the substrate;   means for moving said stage in a direction of an optical axis of said optical system; and   means for exposing light while holding said stage at predetermined plural positions in the direction of the optical axis for a predetermined time, respectively, to perform an exposure operation in such a manner that the image plane of the mask pattern is formed at the plural positions with respect to the stage in the direction of the optical axis..Iaddend..Iadd.15. A reduction projection aligner comprising:   means for holding a mask having a predetermined mask pattern;   a stage for holding a substrate on which a pattern is to be formed;   at least one optical system for projecting said mask pattern onto the substrate; and   a means for forming an image plane of the mask pattern at predetermined plural positions in the direction of an optical axis of said optical system without moving said stage in a direction of said optical axis during an exposure operation in such a manner that the image plane of the mask pattern is formed at said plural positions..Iaddend.