Development of Advanced mask inspection optics with transmitted and reflected light image acquisition

摘要

The lithography potential of an ArF (193nm) laser exposure tool with high numerical aperture (NA) will expand its lithography potential to 65nm node production and even beyond. Consequently, a mask inspection system with a light source, whose wavelength is nearly equal to 193nm, is required so as to detect defects of the masks using resolution enhancement technology (RET). Wavelength consistency between exposure tool and mask inspection tool is strongly required in the field of mask fabrication to obtain high defect inspection sensitivity. Therefore, a novel high-resolution mask inspection platform using DUV wavelength has been developed, which works at 198.5nm. This system has transmission and reflection inspection mode, and throughput using 70nm pixel size were designed within 2 hours per mask. In this paper, transmitted and reflected light image acquisition system and high accuracy focus detection optics are presented.