| 摘要 |
PURPOSE:To automatically correct any defocus and fluctuation in reduction ratio due to fluctuation in atmospheric pressure by a method wherein the relative distance between a reticle, a lens and a wafer is automatically controlled corresponding to any fluctuation in refractive index of air in an optical system due to any environmental changes. CONSTITUTION:Assuming the distance between the centers of a reticle 3 and a lens 5 as well as the refractive index of air respectively to be a and n, the optical path x shall be a/n. Likewise assuming the distance between the lens 9 and a wafer 4 to be b, the optical path y shall be b/n. The refractive index of air may be fluctuated by atmospheric pressure, temperature and humidity however, atmospheric pressure becomes a special issue within a clean room. Any date detected by an atmospheric pressure sensor 20 are inputted into a CPU 21 to process corrected values DELTAa, DELTAb corresponding to any fluctuated atmospheric pressure. DELTAa and DELTAb are respectively transmitted to piezoelement 24 and a driving system 14 as electrical signals to be corrected. Through these procedures, stable exposure characteristics can be maintained constantly regardless of any fluctuation in atmospheric pressure. |
