Focused helium and neon ion beam induced etching for advance EUV lithography and mask repair

The gas field ion microscope was used to investigate helium and neon ion beam induced etching (IBIE) of nickel as a candidate technique for extreme ultraviolet (EUV) lithography mask editing. No discernable nickel etching was observed for room temperature helium exposures at 16 and 30 keV in the range of 1x10$^{\mathrm{15}}$-1x10$^{\mathrm{18}}$ He$^{\mathrm{+}}$/cm$^{\mathrm{2}}$, however transmission electron microscopy (TEM) revealed subsurface damage to the underlying Mo-Si multilayer EUV mirror. Subsequently, neon beam induced etching at 30 keV was investigated over a similar dose range and successfully removed the entire 50 nm nickel top absorber film at a dose of approximately 3x10$^{\mathrm{17}}$ Ne$^{\mathrm{+}}$/cm$^{\mathrm{2}}$. TEM also revealed subsurface damage in the underlying Mo-Si multilayer. To further understand the helium and neon damage, we simulated the ion-solid interactions with our EnvizION Monte Carlo sputtering program which reasonably correlated the observed damage and bubble formation to the nuclear energy loss and the implanted inert gas concentration, respectively. A critical nuclear energy density loss of approximately 80 eV/nm$^{\mathrm{3}}$ and critical implant concentration of approximately 10$^{\mathrm{20}}$ atoms/cm$^{\mathrm{3}}$ have been calculated for damage generation in the multilayer structure.