Analysis of process margin in EUV mask repair with nano-machining

摘要

Reduced design rules demand higher sensitivity of inspection, and thus small defects which did not affect printabilitybefore require repair now. The trend is expected to be similar in extreme ultraviolet lithography (EUVL) which is apromising candidate for sub 32 nm node devices due to high printing resolution. The appropriate repair tool for the smalldefects is a nanomachining system. An area which remains to be studied is the nano-machining system performanceregarding repair of the defects without causing multilayer damage. Currently, nanomachining Z-depth controllability is 3nm while the Ru-capping layer is 2.5 nm thick in a Buffer-less Ru-capped EUV mask. For this report, new repairprocesses are studied in conjunction with the machining behavior of the different EUVL mask layers. Repair applicationsto achieve the Edge Placement(EP) and Z-depth controllability for an optimal printability process window are discussed.Repair feasibility was determined using a EUV micro exposure tool (MET) and Actinic Imaging Tool (AIT) to evaluaterepairs the 30 nm and 40 nm nodes. Finally, we will report the process margin of the repair through Slitho-EUVTMsimulation by controlling side wall angle, Z-depth, and EP (Edge Placement) on the base of 3-dimensional experimentalresult.