| 摘要 |
A high-performance projection optical system uses the multiple spectral peaks of an excimer laser system by using an optical dispersive system to physically separate the broadband laser output into separate narrowband beams which can be used for imaging different substrate surfaces simultaneously. The separated narrowband beams are directed along different optical paths and used to illuminate the object planes of different, identical projection lenses. The projection lenses are designed for the narrowed bandwidth corresponding to one spectral peak of the excimer laser rather than the broadband, multiple-peak laser output This dramatically simplifies both the design and the construction of the projection lens, leading to substantial cost-savings. The conversion of the single-beam, broadband spectral output into a multiple-beam, narrowband source is accomplished by optical dispersion means consisting of either several prisms in series, one or more prisms followed by a mirror reflecting back through the prisms, or one or more reflective gratings. The separated narrowband beams are useful for imaging top and bottom of a single substrate with exact registration useful for via-hole connections. Other uses include simultaneous imaging of multiple substrates, using one or more stages.
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