Optomechanical characterization of large wafer stepper-optics with respect to centering errors, lens distances and center thicknesses

摘要

One key technology in mass microchip-production is an optical projection system (wafer stepper) for deep UV photolithography. Modern wafer stepper-optics featuring sub-200nm resolution, consist of 20 to 25 glass elements with a weight of up to 1000 kg. After the careful glass element-manufacturing, the optical performance of the system is highly influenced by the precise mechanical alignment of all individual lens elements. The imaging quality of such systems is extremely sensitive to centering errors as they may severely degrade the imaging quality. Therefore, the optical design of a stepper optic is tightly toleranced for the alignment in the sub-um and arc second range.