Inhibiting spontaneous etching of nanoscale electron beam induced etching features: Solutions for nanoscale repair of extreme ultraviolet lithography masks

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.