Nanoparticle removal from EUV photomasks using laser induced plasma shockwaves

Abstract

In recent years, it has been demonstrated that nanoparticles can be detached and removed from substrates using laser-induced plasma (LIP) shockwaves. While it was experimentally established the effectiveness of the LIP technique for removing nanoparticles in the sub-100nm range, the removal mechanisms were not well-understood. In this article, we introduce a set of particle removal mechanisms based on moment resistance of the particle-substrate bond and discuss their effectiveness and applicability in laser-induced plasma shock nanoparticle removal. The mechanical interactions between nanoparticles and shockwaves are studied by utilizing molecular dynamic simulation approach. The forces and moments acting on nanoparticles are calculated and are related to the detachment mechanisms. It is demonstrated that sub-100nm particles can be detached from various substrates. Experiments and simulations are performed to study the effect of LIP on optical and EUVL/LTEM substrates in terms of substrate damage. Initial experiments and simulations reveal the window of safe operation of LIP and the mechanisms responsible for material alterations if any at close distances of operation of LIP above the substrate.