Native pattern defect inspection of EUV mask using advanced electron beam inspection system

Abstract

Fabrication of defect free EUV mask is one of the most critical roadblocks for implementing EUV lithography into semiconductor high volume manufacturing for 22nm half-pitch (HP) node and beyond. At the same time, development of quality assurance process for the defect free EUV mask is also another critical challenge we need to address before the mass production. Inspection tools act important role in quality assurance process to ensure the defect free EUV mask. We are currently evaluating two types of inspection system: optical inspection (OPI) system and electron beam inspection (EBI) system [1, 2]. While OPI system is sophisticated technology and has an advantage in throughput, EBI system is superior in sensitivity and extendability to even small pattern. We evaluated sensitivity of EBI system and found it could detect 25 nm defects on 88nm L/S pattern which is as small as target defect size for 23 nm Flash HP pattern in 2013 in 2009 ITRS lithography roadmap [2, 3]. EBI system is effective inspection tool even at this moment to detect such small defects on 88nm HP pattern, though there are still some challenges such as the slow throughput and the reliability. Therefore, EBI system can be used as bridge tool to compensate insufficient sensitivity of current inspection tools and improve EUV mask fabrication process to achieve the defect free EUV mask. In this paper, we will present the results of native pattern defects founded on large field 88nm HP pattern using advance EBI system. We will also classify those defects and propose some ideas to mitigate them and realize the defect free EUV mask, demonstrating the capability of EBI as bridge tool.