Nanomachining is typically described as being a material-independent subtractive mask repair process. This is a correct statement, for the most part, since it does not require a material end-stop nor chemistries targeted to remove only a specific material. However, it is not true when considering the effect of materials being removed on the integrity of the nanomachining tip (also referred to here as NanoBitsTM). While many advanced absorber materials such as OMOG are easier to nanomachine than earlier absorber materials such as chrome and MoSi, the absorbers used in EUV have proven to be much harder and tougher (in a nanomechanical sense) while sitting atop a very fragile multilayer substrate. This work shows results from advancements on the latest nanomachining platform, nm-VI to minimize tip wear during the repair process. Consequently, this improves defect repair capability for smaller dimensions, decreases overhead from tip changeouts, decreases the cost of consumables by increasing NanoBit lifetime, and increases repair tool return-on-investment.
Nanomachining is one of the primary repair processes for leading-edge technology photomasks. Many hardware improvements have been made in successive nanomachining-tool generations to improve repair performance specifications (stability, drift, and z-depth control). However, improvement to the repair processes are still needed to address the use of the latest generation of high aspect-ratio (HAR) NanoBitsTM (1.8 AR and above). Although beneficial for repair of leading-edge photomasks, HAR NanoBitsTM exhibit greater degrees of nonlinear deflection, wear, and even breakage during traditional repair processes. In this work, the authors chronicle investigations into new nanomachining process options to enable subtractive hard defect repair with HAR NanoBitsTM down to the most advanced technology node with topographic z-depth control within ±0.5 nm and no detectable line edge, or multilayer capping layer, roughness.
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