Apparatus for detecting a focussing position
First Claim
1. An apparatus for detecting a position of a conjugate plane at which a projected image of an object surface is formed by a projection optical system or a focussing position, said apparatus comprising:
- projection object means including at least a first surface having reflecting properties and arranged on said object surface;
stage means for holding a photosensing substrate having a photosensing surface to be positioned at said conjugate plane in a manner that said photosensing substrate is movable in the direction of an optical axis of said projection optical system;
reference surface means provided on said stage means and adapted to be arranged on the basis of a position conjugate to said first surface arranged on said object surface with respect to said projection optical system;
a transparent pattern of a predetermined configuration formed on a surface of said reference surface means;
illuminating means for supplying an illuminating light through said transparent pattern in such a manner that said illuminating light reaches said first surface from said transparent pattern through said projection optical system;
means for receiving a reflected light of said illuminating light from said first surface through said projection optical system and said transparent pattern; and
detecting means for detecting a variation in the light quantity of said reflected light received by said means.
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Abstract
An apparatus for detecting a focussing position in a projection exposure system. The apparatus constitutes a detection system for causing the so-called automatic focussing apparatus to operate more precisely with greater reliability and the focussing height at the respective portions of a mask pattern are separately determined, thereby making the accurate discrimination of the focussing position even in cases where any special mark is not used or the intentity of the exposure light is varied moment by moment. This apparatus includes a reference surface formed with a transparent pattern of a given configuration and provided on a stage, an illuminating system for directing an illuminating light to the transparent pattern, and a detection system whereby the reflected light from the mask pattern surface of the projected image of the transparent pattern formed by the projection optical system under the application of the illuminating light is detected through the projection optical system and the transparent pattern thereby detecting a variation in the light quantity of the reflected light. The position (height) where the light quantity variation of the reflected light attains the maximum or minimum represents the focussing position.
43 Citations
12 Claims
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1. An apparatus for detecting a position of a conjugate plane at which a projected image of an object surface is formed by a projection optical system or a focussing position, said apparatus comprising:
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projection object means including at least a first surface having reflecting properties and arranged on said object surface; stage means for holding a photosensing substrate having a photosensing surface to be positioned at said conjugate plane in a manner that said photosensing substrate is movable in the direction of an optical axis of said projection optical system; reference surface means provided on said stage means and adapted to be arranged on the basis of a position conjugate to said first surface arranged on said object surface with respect to said projection optical system; a transparent pattern of a predetermined configuration formed on a surface of said reference surface means; illuminating means for supplying an illuminating light through said transparent pattern in such a manner that said illuminating light reaches said first surface from said transparent pattern through said projection optical system; means for receiving a reflected light of said illuminating light from said first surface through said projection optical system and said transparent pattern; and detecting means for detecting a variation in the light quantity of said reflected light received by said means. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An exposure apparatus for projecting and exposing a pattern formed on a pattern surface of a mask on a surface of a substrate by a projection optical system, said apparatus comprising:
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first stage means for supporting said mask; second stage means for supporting said photosensitive substrate; first illuminating means for illuminating said mask with an exposure light; first measuring means for detecting a position of said substrate in the direction of an optical axis of said projection optical system; means responsive to a signal from said first measuring means to adjust a space between said projection optical system and said substrate and thereby to position said substrate at an image plane position of said projection optical system; reference surface means provided on said second stage means and adapted to be arranged on the basis of a position conjugate to said master pattern surface arranged on an object surface with respect to said projection optical system; a transparent pattern of a predetermined configuration formed on a surface of said reference surface means; second illuminating means for supplying an illuminating light through said transparent pattern so as to reach said mask pattern surface from said transparent pattern through said projection optical system; means for receiving a reflected light of said illuminating light from said mask pattern surface through said projection optical system and said transparent pattern; and detecting means for detecting a variation in the light quantity of said reflected light received by said for receiving a reflected light means. - View Dependent Claims (9, 10, 11, 12)
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Specification