ABSTRACT
Withcurrentlithographymasks,particlecontaminationofthestructuredareais preventedbyaprotectiveandtransparentpellicle,keepingparticulatematterout ofthefocusplane.Inextreme-UV(EUV)lithography,nosuitablepelliclematerialisavailableand,therefore,thestructuredareaisunprotected.Particlesas smallas30nmpresentaseriousrisk,astheymayleadtoprintabledefects.Particle-freemaskscanbeachievedbyeitherpreventionofcontaminationorbycleaningcontaminatedreticles.Preventivestrategiesincludepreventionofparticle generationandpreventionofdepositionintheEUVtool[1],aswellasinprecedingsteps.
