The study of EUVL mask defect inspection technology for 32-nm half-pitch node device and beyond

摘要

In this paper, we will report on our experimental and simulation results on the impact of EUVL mask absorberstructure and of inspection system optics on mask defect detection sensitivity. We employed a commercial simulatorEM-Suite (Panoramic Technology, Inc.) which calculated rigorously using FDTD (Finite-difference time-domain)method. By using various optical constants of absorber stacks, we calculated image contrasts and defect image signals asobtained from the mask defect inspection system. We evaluated the image contrast and the capability of detectingdefects on the EUVL masks by using a new inspection tool made by NuFlare Technology, Inc. (NFT) and AdvancedMask Inspection Technology, Inc. (AMiT). This tool is based on NPI-5000 which is the leading—edge photomask defectinspection system using 199nm wavelength inspection optics. The programmed defect masks with LR-TaBN and LR-TaSi absorbers were used which had various sized opaque and clear extension defects on hp-160nm, hp-225nm, and hp-325nm line and space patterns. According to the analysis, reflectivity of EUVL mask absorber structures and theinspection optics have large influence on image contrast and defect sensitivity. It is very important to optimize absorberstructure and inspection optics for the development of EUVL mask inspection technology, and for the improvement ofperformance of EUV lithographic systems.