| 摘要 |
<p>PURPOSE:To cause a pattern formed on a substrate to coincide always precisely with a projecting pattern to be printed, with it overlapped, by defining a space for sealing gas with a refractive index different from that of the air in a projecting optical system, and by changing distance of the sealed space to correct the optical path length. CONSTITUTION:An optical image of an original pattern such as circuit elements drawn on a reticle R is passed through transparent thin films (pellicles) 3a, 3b which are arrayed in parallel in the air with a distance (t), is reduced at a given reduction rate R by a reducing projection lens 4, and is focussed on a wafer W being placed on the stage 5. Holding frames 6, 7 are coupled each other by expandable and contractible bellows 8 so that the space put between the pellicles 3a, 3b can beome a sealed space being interrupted from the outside. Driving the motor 9 can change a relative distance between the holding frames 6 and 7, that is, a distance between the pellicles 3a and 3b in the optical axis Ax direction. Since gas containing ingredients different from the ingredients of the outside air is housed in the sealed space and the gas reservoir 17, and has a refractive index different from that of the outside air, the parallel planes can serve as optical path correcting means.</p> |
