EUV stochastic defect monitoring with advanced broadband optical wafer inspection and e-beam review systems

As Extreme UltraViolet (EUV) lithography nears high volume manufacturing (HVM) adoption to enable the sub-7nm scaling roadmap, characterizing and monitoring defects that print at wafer level are of critical importance to yield. This is especially true for defects coming from the EUV mask, such as multi-layer defects, added particles or growth on mask, and for defects coming from the pattern formation process itself, also referred to as stochastic printing defects. A “Print Check” solution has been previously described.1 This technique uses full-wafer patterned optical inspection to monitor mask defects that print on the wafer. In this paper we focus on developing metrology solutions for stochastic printing defects, which are random local variations that occur between structures that should, in principle, print identically, but actually occur at significant frequencies with current state-of-the-art processes. Specifically, we discuss the importance of monitoring these defects using broadband plasma optical inspection and e-beam defect review systems. We show extensive characterizations of defects on line space patterns down to a pitch of 36nm, on contact holes at a pitch of 48nm and on logic blocks in a foundry equivalent N5 test vehicle. Analysis methods based on CD SEM and review SEM images have been described.