| 摘要 |
An improved step and repeat alignment and exposure system for printing an image of a reticle onto a semiconductive wafer. A projection lens, such as a unit magnification catadioptric lens, projects the reticle image onto the semiconductive wafer. Novel viewing port means provide a direct view of a portion of the semiconductive wafer which portion has been illuminated by the projected reticle image. In one embodiment a viewing port is formed in the mirror of a catadioptric lens by way of either a physical aperture or transmissive coatings. Off axis viewing of images through the viewing port is provided to provide telecentric images. Means are also provided for calibrating the position of the stage with respect to the reticle. Means are provided for determining offset values between the projected reticle image and the stage reference mark and for utilizing said offsets in controlling the position of the stage. A novel reticle alignment window array and alignment mark are disclosed which provide both direction and degree of misalignment information without the requirement of relative motion between the reticle and semiconductive wafer. Also employed is a subsystem which is responsive to the relative amounts of light being provided in the image of the alignment mark as a function of the proportion of the alignment mark being illuminated by the images of each of the alignment windows in the array so that a real-time alignment correction can be obtained.
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