Raster-scan photolithographic reduction system
First Claim
Patent Images
1. A reduction photolithography system using a reduction lens forming a circular image field in a plane of a substrate to be imaged and an illumination system for shaping the image field to a hexagonal configuration for raster scanning, the system comprising:
- a. the illumination system being variable for providing the hexagonal configuration with different length sides subtending different angles and disposed as cords of the circular field;
b. a pair of parallel and equal length sides of the hexagonal configuration being disposed perpendicular to a scan direction and having variable lengths that establish a width of a full-exposure region of a scan; and
c. a pair of congruent isosceles triangles having bases parallel with the scan direction and extending between ends of the parallel sides, and the triangles providing half-exposure regions for overlap of successive scans.
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Abstract
A reduction photolithographic scanning system uses a reduction lens with a circular image field that is shaped to an irregular hexagonal configuration affording different effective scanning widths so that the full area of a microcircuit image can be scanned onto a substrate in an integer number of overlapping scans. This minimizes the number of scans required for each image area and maximizes the total image area that can be scanned per time unit.
47 Citations
37 Claims
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1. A reduction photolithography system using a reduction lens forming a circular image field in a plane of a substrate to be imaged and an illumination system for shaping the image field to a hexagonal configuration for raster scanning, the system comprising:
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a. the illumination system being variable for providing the hexagonal configuration with different length sides subtending different angles and disposed as cords of the circular field; b. a pair of parallel and equal length sides of the hexagonal configuration being disposed perpendicular to a scan direction and having variable lengths that establish a width of a full-exposure region of a scan; and c. a pair of congruent isosceles triangles having bases parallel with the scan direction and extending between ends of the parallel sides, and the triangles providing half-exposure regions for overlap of successive scans. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A reduction photolithographic system using a reduction lens forming a circular image field at a plane of a substrate to be imaged from a reticle, and an illuminating system for shaping the image field to a hexagonal configuration for raster scanning a microcircuit pattern of the reticle onto the substrate, the system comprising:
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a. the hexagonal configuration of the image field being variably irregular so that sides of the hexagonal configuration having different lengths are arranged as cords of the circular image field which is smaller than a region of the substrate exposed to an image of the microcircuit pattern; and b. two parallel and opposite sides of the hexagonal configuration being variable in height and disposed perpendicular to a scan direction, the variable height of the opposite sides being selected so that the hexagonal configuration can scan a full image of the microcircuit pattern uniformly onto the region of the substrate in an integer number of substantially equal scans. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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15. In a raster-scan system for reduction photolithography using a catadioptric reduction lens having a circular image field at a plane of a substrate to be imaged from a reticle pattern for a microcircuit device and an illumination system for shaping the image field to a configuration that allows raster scanning, the improvement comprising:
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a. the image field being formed as an irregular polygon having sides disposed as cords of the circular image field, the sides having variable lengths selected so that an integer number of scans of a viewing field of the lens across the reticle pattern images the reticle pattern uniformly on the substrate with each of the scans being substantially equal; and b. the reduction lens being achromatized over a range of a deep UV source of actinic radiation and having a reduction element with a concave half-reflecting external surface and a concave fully reflecting internal surface with a central aperture upstream of the image field. - View Dependent Claims (16, 17, 18, 19, 20)
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21. A reduction photolithographic raster-scanning method comprising:
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a. variably illuminating a circular image field of a reduction lens to form the image field as an irregular hexagon having variable length sides disposed as cords of the circular image field; and b. dimensioning the sides of the hexagon to form successive scans of full-exposure regions of the hexagon and overlapped half-exposure regions of the hexagon that uniformly expose a full area of a microcircuit pattern onto a region of a substrate in an integer number of substantially equal scans. - View Dependent Claims (22, 23, 24, 25)
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26. A method of raster scanning a reduced image of a microcircuit reticle pattern onto a substrate for photolithographic purposes, the method using a catadioptric reduction lens having a circular image field at a plane of the substrate, and the method comprising:
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a. confining illumination of the circular image field to a region within cords forming an irregular hexagon having corners intersecting the circular image field; and b. varying the length of parallel cords of the hexagon disposed perpendicular to a scanning direction so that exposure of the substrate from overlapped scans of the hexagon uniformly images the full area of the microcircuit pattern onto the substrate in an integer number of substantially equal scans. - View Dependent Claims (27, 28, 29, 30, 31)
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32. A reduction photolithographic system for imaging a reticle pattern of a microcircuit device onto a substrate with a reduction lens having a circular image field smaller than a region of the substrate exposed to the reticle pattern, the system comprising:
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a. an illumination system for shaping the image field to an irregular hexagonal shape having sides disposed as cords of the image field; b. a portion of the hexagonal shape between parallel sides oriented perpendicular to a scan direction forming a full exposure of a portion of the reticle pattern onto a corresponding portion of the substrate region with each scan; c. overlapping half-exposure regions of the hexagonal shape being positioned for double exposing portions of the reticle pattern onto the substrate region in zones between successive scans; and d. dimensions of the irregular hexagonal shape being selected so that the full exposure portions and the double exposing portions combine for uniformly exposing the substrate region to the full reticle pattern in an integer number of substantially equal scans. - View Dependent Claims (33, 34, 35, 36, 37)
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Specification