| 摘要 |
PURPOSE:To observe an alignment mark on a wafer at all times, and to conduct alignment with high precision by arranging one part of a wafer-surface observation optical system between the optical system and a reticle and turning an objective constituting one part of the optical system in an arcuate shape with respect to the optical axis of a projection optical system. CONSTITUTION:Observation system objectives 4A-4D and reflecting mirrors 5A-5D are disposed movably in an arcuate 20 shape centering around an optical-system optical axis O between a reticle 1 and a photographing optical system 2, and the lenses 4A-4B, 4C-4D are paired and the scribing line of a wafer 3 is observed. The quantities of displacement are computed at every shot by the photoelectric signals of elements 10A, 10B through the lenses 4A, 4B by an alignment mark 13 on the line. The quantities of displacement detected are compensated by adjusting the correlation of the wafer and the reticle on the basis of the known quantity of displacement of the position of alignment and the position of printing and the wafer is exposed. Measurement is conducted during scanning in the direction of main stepping, the two alignment marks 13 are measured simultaneously, alignment and printing can be performed at high speed, and the precision of alignment is increased by repeating measurement. The two objectives advantageous for executing stepping are selected, thus improving a throughput. |
