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Phase defects that introduce errors in the printed image are one of the major yield limiters for reticles in extreme-ultraviolet lithography. The basis for a reticle is a mask blank, consisting of an ultra-low-expansion substrate and a reflective multilayer stack that is made up of Mo and Si. A potential methodology for repairing phase defects in these mask blanks is to locally irradiate it with a high-resolution electron beam to induce structural deformations that cancel out the distortion of the multilayer. We present experimental and modeling results that show that the interaction of an electron beam with a mask blank can only be understood when the contraction of the multilayer through silicide formation and substrate compaction, as well as the mechanical response of the mask blank, are considered. One of the consequences is that electron beams with energies around 10 keV that are less than 20 nm in diameter induce depressions in multilayers made up of 50 Mo/Si bilayers that have a surprisingly large diameter of about a micrometer. Our models suggest that these unacceptably large diameters can only be reduced if the compaction of the substrate is prevented. [ABSTRACT FROM AUTHOR]

Electron beam induced etching (EBIE) is an important technique for repairing nanoscale defects on extreme ultraviolet (EUV) lithography masks as it provides excellent spatial resolution and etch selectivity while minimizing collateral damage to the mask. While EBIE itself is a complex process, a current problem with EBIE of the TaN EUV mask absorber layer using XeF2 is the spontaneous etching of repaired features during subsequent edits of the mask. This work explores three passivation techniques for controlling the spontaneous etching after an EBIE repair is made. An oxygen plasma was used to attempt to oxidize the TaN sidewalls, but it was not successful at stopping the spontaneous etching. An active electron beam induced passivation using water was successful at stopping the spontaneous etching. Also, simple adsorption of water molecules on the TaN sidewalls was successful at inhibiting spontaneous etching. The successful passivation strategies are affected by subsequent scanning electron beam imaging. It was determined that the electron beam activated passivation can be damaged by electron beam imaging in the presence of residual XeF2 on the surface. Also, the adsorbed water passivation strategy is susceptible to electron induced desorption of the water. [ABSTRACT FROM AUTHOR]